HTML 5.1

4.10 Forms

4.10.1 Introduction

This section is non-normative.

A form is a component of a Web page that has form controls, such as text fields, buttons, checkboxes, range controls, or color pickers. A user can interact with such a form, providing data that can then be sent to the server for further processing (e.g. returning the results of a search or calculation). No client-side scripting is needed in many cases, though an API is available so that scripts can augment the user experience or use forms for purposes other than submitting data to a server.

Writing a form consists of several steps, which can be performed in any order: writing the user interface, implementing the server-side processing, and configuring the user interface to communicate with the server.

4.10.1.1 Writing a form's user interface

This section is non-normative.

For the purposes of this brief introduction, we will create a pizza ordering form.

Any form starts with a form element, inside which are placed the controls. Most controls are represented by the input element, which by default provides a one-line text field. To label a control, the label element is used; the label text and the control itself go inside the label element. Each part of a form is considered a paragraph, and is typically separated from other parts using p elements. Putting this together, here is how one might ask for the customer's name:

<form>
 <p><label>Customer name: <input></label></p>
</form>

To let the user select the size of the pizza, we can use a set of radio buttons. Radio buttons also use the input element, this time with a type attribute with the value radio. To make the radio buttons work as a group, they are given a common name using the name attribute. To group a batch of controls together, such as, in this case, the radio buttons, one can use the fieldset element. The title of such a group of controls is given by the first element in the fieldset, which has to be a legend element.

<form>
 <p><label>Customer name: <input></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size> Small </label></p>
  <p><label> <input type=radio name=size> Medium </label></p>
  <p><label> <input type=radio name=size> Large </label></p>
 </fieldset>
</form>

Changes from the previous step are highlighted.

To pick toppings, we can use checkboxes. These use the input element with a type attribute with the value checkbox:

<form>
 <p><label>Customer name: <input></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size> Small </label></p>
  <p><label> <input type=radio name=size> Medium </label></p>
  <p><label> <input type=radio name=size> Large </label></p>
 </fieldset>
 <fieldset>
  <legend> Pizza Toppings </legend>
  <p><label> <input type=checkbox> Bacon </label></p>
  <p><label> <input type=checkbox> Extra Cheese </label></p>
  <p><label> <input type=checkbox> Onion </label></p>
  <p><label> <input type=checkbox> Mushroom </label></p>
 </fieldset>
</form>

The pizzeria for which this form is being written is always making mistakes, so it needs a way to contact the customer. For this purpose, we can use form controls specifically for telephone numbers (input elements with their type attribute set to tel) and e-mail addresses (input elements with their type attribute set to email):

<form>
 <p><label>Customer name: <input></label></p>
 <p><label>Telephone: <input type=tel></label></p>
 <p><label>E-mail address: <input type=email></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size> Small </label></p>
  <p><label> <input type=radio name=size> Medium </label></p>
  <p><label> <input type=radio name=size> Large </label></p>
 </fieldset>
 <fieldset>
  <legend> Pizza Toppings </legend>
  <p><label> <input type=checkbox> Bacon </label></p>
  <p><label> <input type=checkbox> Extra Cheese </label></p>
  <p><label> <input type=checkbox> Onion </label></p>
  <p><label> <input type=checkbox> Mushroom </label></p>
 </fieldset>
</form>

We can use an input element with its type attribute set to time to ask for a delivery time. Many of these form controls have attributes to control exactly what values can be specified; in this case, three attributes of particular interest are min, max, and step. These set the minimum time, the maximum time, and the interval between allowed values (in seconds). This pizzeria only delivers between 11am and 9pm, and doesn't promise anything better than 15 minute increments, which we can mark up as follows:

<form>
 <p><label>Customer name: <input></label></p>
 <p><label>Telephone: <input type=tel></label></p>
 <p><label>E-mail address: <input type=email></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size> Small </label></p>
  <p><label> <input type=radio name=size> Medium </label></p>
  <p><label> <input type=radio name=size> Large </label></p>
 </fieldset>
 <fieldset>
  <legend> Pizza Toppings </legend>
  <p><label> <input type=checkbox> Bacon </label></p>
  <p><label> <input type=checkbox> Extra Cheese </label></p>
  <p><label> <input type=checkbox> Onion </label></p>
  <p><label> <input type=checkbox> Mushroom </label></p>
 </fieldset>
 <p><label>Preferred delivery time: <input type=time min="11:00" max="21:00" step="900"></label></p>
</form>

The textarea element can be used to provide a free-form text field. In this instance, we are going to use it to provide a space for the customer to give delivery instructions:

<form>
 <p><label>Customer name: <input></label></p>
 <p><label>Telephone: <input type=tel></label></p>
 <p><label>E-mail address: <input type=email></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size> Small </label></p>
  <p><label> <input type=radio name=size> Medium </label></p>
  <p><label> <input type=radio name=size> Large </label></p>
 </fieldset>
 <fieldset>
  <legend> Pizza Toppings </legend>
  <p><label> <input type=checkbox> Bacon </label></p>
  <p><label> <input type=checkbox> Extra Cheese </label></p>
  <p><label> <input type=checkbox> Onion </label></p>
  <p><label> <input type=checkbox> Mushroom </label></p>
 </fieldset>
 <p><label>Preferred delivery time: <input type=time min="11:00" max="21:00" step="900"></label></p>
 <p><label>Delivery instructions: <textarea></textarea></label></p>
</form>

Finally, to make the form submittable we use the button element:

<form>
 <p><label>Customer name: <input></label></p>
 <p><label>Telephone: <input type=tel></label></p>
 <p><label>E-mail address: <input type=email></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size> Small </label></p>
  <p><label> <input type=radio name=size> Medium </label></p>
  <p><label> <input type=radio name=size> Large </label></p>
 </fieldset>
 <fieldset>
  <legend> Pizza Toppings </legend>
  <p><label> <input type=checkbox> Bacon </label></p>
  <p><label> <input type=checkbox> Extra Cheese </label></p>
  <p><label> <input type=checkbox> Onion </label></p>
  <p><label> <input type=checkbox> Mushroom </label></p>
 </fieldset>
 <p><label>Preferred delivery time: <input type=time min="11:00" max="21:00" step="900"></label></p>
 <p><label>Delivery instructions: <textarea></textarea></label></p>
 <p><button>Submit order</button></p>
</form>

4.10.1.2 Implementing the server-side processing for a form

This section is non-normative.

The exact details for writing a server-side processor are out of scope for this specification. For the purposes of this introduction, we will assume that the script at https://pizza.example.com/order.cgi is configured to accept submissions using the application/x-www-form-urlencoded format, expecting the following parameters sent in an HTTP POST body:

custname

Customer's name

custtel

Customer's telephone number

custemail

Customer's e-mail address

size

The pizza size, either small, medium, or large

topping

A topping, specified once for each selected topping, with the allowed values being bacon, cheese, onion, and mushroom

delivery

The requested delivery time

comments

The delivery instructions

4.10.1.3 Configuring a form to communicate with a server

This section is non-normative.

Form submissions are exposed to servers in a variety of ways, most commonly as HTTP GET or POST requests. To specify the exact method used, the method attribute is specified on the form element. This doesn't specify how the form data is encoded, though; to specify that, you use the enctype attribute. You also have to specify the URL of the service that will handle the submitted data, using the action attribute.

For each form control you want submitted, you then have to give a name that will be used to refer to the data in the submission. We already specified the name for the group of radio buttons; the same attribute (name) also specifies the submission name. Radio buttons can be distinguished from each other in the submission by giving them different values, using the value attribute.

Multiple controls can have the same name; for example, here we give all the checkboxes the same name, and the server distinguishes which checkbox was checked by seeing which values are submitted with that name — like the radio buttons, they are also given unique values with the value attribute.

Given the settings in the previous section, this all becomes:

<form method="post"
      enctype="application/x-www-form-urlencoded"
      action="https://pizza.example.com/order.cgi">
 <p><label>Customer name: <input name="custname"></label></p>
 <p><label>Telephone: <input type=tel name="custtel"></label></p>
 <p><label>E-mail address: <input type=email name="custemail"></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size value="small"> Small </label></p>
  <p><label> <input type=radio name=size value="medium"> Medium </label></p>
  <p><label> <input type=radio name=size value="large"> Large </label></p>
 </fieldset>
 <fieldset>
  <legend> Pizza Toppings </legend>
  <p><label> <input type=checkbox name="topping" value="bacon"> Bacon </label></p>
  <p><label> <input type=checkbox name="topping" value="cheese"> Extra Cheese </label></p>
  <p><label> <input type=checkbox name="topping" value="onion"> Onion </label></p>
  <p><label> <input type=checkbox name="topping" value="mushroom"> Mushroom </label></p>
 </fieldset>
 <p><label>Preferred delivery time: <input type=time min="11:00" max="21:00" step="900" name="delivery"></label></p>
 <p><label>Delivery instructions: <textarea name="comments"></textarea></label></p>
 <p><button>Submit order</button></p>
</form>

There is no particular significance to the way some of the attributes have their values quoted and others don't. The HTML syntax allows a variety of equally valid ways to specify attributes, as discussed in the syntax section.

For example, if the customer entered "Denise Lawrence" as their name, "555-321-8642" as their telephone number, did not specify an e-mail address, asked for a medium-sized pizza, selected the Extra Cheese and Mushroom toppings, entered a delivery time of 7pm, and left the delivery instructions text field blank, the user agent would submit the following to the online Web service:

custname=Denise+Lawrence&custtel=555-321-8624&custemail=&size=medium&topping=cheese&topping=mushroom&delivery=19%3A00&comments=

4.10.1.4 Client-side form validation

This section is non-normative.

Forms can be annotated in such a way that the user agent will check the user's input before the form is submitted. The server still has to verify the input is valid (since hostile users can easily bypass the form validation), but it allows the user to avoid the wait incurred by having the server be the sole checker of the user's input.

The simplest annotation is the required attribute, which can be specified on input elements to indicate that the form is not to be submitted until a value is given. By adding this attribute to the customer name, pizza size, and delivery time fields, we allow the user agent to notify the user when the user submits the form without filling in those fields:

<form method="post"
      enctype="application/x-www-form-urlencoded"
      action="https://pizza.example.com/order.cgi">
 <p><label>Customer name: <input name="custname" required></label></p>
 <p><label>Telephone: <input type=tel name="custtel"></label></p>
 <p><label>E-mail address: <input type=email name="custemail"></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size required value="small"> Small </label></p>
  <p><label> <input type=radio name=size required value="medium"> Medium </label></p>
  <p><label> <input type=radio name=size required value="large"> Large </label></p>
 </fieldset>
 <fieldset>
  <legend> Pizza Toppings </legend>
  <p><label> <input type=checkbox name="topping" value="bacon"> Bacon </label></p>
  <p><label> <input type=checkbox name="topping" value="cheese"> Extra Cheese </label></p>
  <p><label> <input type=checkbox name="topping" value="onion"> Onion </label></p>
  <p><label> <input type=checkbox name="topping" value="mushroom"> Mushroom </label></p>
 </fieldset>
 <p><label>Preferred delivery time: <input type=time min="11:00" max="21:00" step="900" name="delivery" required></label></p>
 <p><label>Delivery instructions: <textarea name="comments"></textarea></label></p>
 <p><button>Submit order</button></p>
</form>

It is also possible to limit the length of the input, using the maxlength attribute. By adding this to the textarea element, we can limit users to 1000 characters, preventing them from writing huge essays to the busy delivery drivers instead of staying focused and to the point:

<form method="post"
      enctype="application/x-www-form-urlencoded"
      action="https://pizza.example.com/order.cgi">
 <p><label>Customer name: <input name="custname" required></label></p>
 <p><label>Telephone: <input type=tel name="custtel"></label></p>
 <p><label>E-mail address: <input type=email name="custemail"></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size required value="small"> Small </label></p>
  <p><label> <input type=radio name=size required value="medium"> Medium </label></p>
  <p><label> <input type=radio name=size required value="large"> Large </label></p>
 </fieldset>
 <fieldset>
  <legend> Pizza Toppings </legend>
  <p><label> <input type=checkbox name="topping" value="bacon"> Bacon </label></p>
  <p><label> <input type=checkbox name="topping" value="cheese"> Extra Cheese </label></p>
  <p><label> <input type=checkbox name="topping" value="onion"> Onion </label></p>
  <p><label> <input type=checkbox name="topping" value="mushroom"> Mushroom </label></p>
 </fieldset>
 <p><label>Preferred delivery time: <input type=time min="11:00" max="21:00" step="900" name="delivery" required></label></p>
 <p><label>Delivery instructions: <textarea name="comments" maxlength=1000></textarea></label></p>
 <p><button>Submit order</button></p>
</form>

When a form is submitted, invalid events are fired at each form control that is invalid, and then at the form element itself. This can be useful for displaying a summary of the problems with the form, since typically the browser itself will only report one problem at a time.

4.10.1.5 Enabling client-side automatic filling of form controls

This section is non-normative.

Some browsers attempt to aid the user by automatically filling form controls rather than having the user reenter their information each time. For example, a field asking for the user's telephone number can be automatically filled with the user's phone number.

To help the user agent with this, the autocomplete attribute can be used to describe the field's purpose. In the case of this form, we have three fields that can be usefully annotated in this way: the information about who the pizza is to be delivered to. Adding this information looks like this:

<form method="post"
      enctype="application/x-www-form-urlencoded"
      action="https://pizza.example.com/order.cgi">
 <p><label>Customer name: <input name="custname" required autocomplete="shipping name"></label></p>
 <p><label>Telephone: <input type=tel name="custtel" autocomplete="shipping tel"></label></p>
 <p><label>E-mail address: <input type=email name="custemail" autocomplete="shipping email"></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size required value="small"> Small </label></p>
  <p><label> <input type=radio name=size required value="medium"> Medium </label></p>
  <p><label> <input type=radio name=size required value="large"> Large </label></p>
 </fieldset>
 <fieldset>
  <legend> Pizza Toppings </legend>
  <p><label> <input type=checkbox name="topping" value="bacon"> Bacon </label></p>
  <p><label> <input type=checkbox name="topping" value="cheese"> Extra Cheese </label></p>
  <p><label> <input type=checkbox name="topping" value="onion"> Onion </label></p>
  <p><label> <input type=checkbox name="topping" value="mushroom"> Mushroom </label></p>
 </fieldset>
 <p><label>Preferred delivery time: <input type=time min="11:00" max="21:00" step="900" name="delivery" required></label></p>
 <p><label>Delivery instructions: <textarea name="comments" maxlength=1000></textarea></label></p>
 <p><button>Submit order</button></p>
</form>

4.10.1.6 Improving the user experience on mobile devices

This section is non-normative.

Some devices, in particular those with on-screen keyboards and those in locales with languages with many characters (e.g. Japanese), can provide the user with multiple input modalities. For example, when typing in a credit card number the user may wish to only see keys for digits 0-9, while when typing in their name they may wish to see a form field that by default capitalises each word.

Using the inputmode attribute we can select appropriate input modalities:

<form method="post"
      enctype="application/x-www-form-urlencoded"
      action="https://pizza.example.com/order.cgi">
 <p><label>Customer name: <input name="custname" required autocomplete="shipping name" inputmode="latin-name"></label></p>
 <p><label>Telephone: <input type=tel name="custtel" autocomplete="shipping tel"></label></p>
 <p><label>E-mail address: <input type=email name="custemail" autocomplete="shipping email"></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size required value="small"> Small </label></p>
  <p><label> <input type=radio name=size required value="medium"> Medium </label></p>
  <p><label> <input type=radio name=size required value="large"> Large </label></p>
 </fieldset>
 <fieldset>
  <legend> Pizza Toppings </legend>
  <p><label> <input type=checkbox name="topping" value="bacon"> Bacon </label></p>
  <p><label> <input type=checkbox name="topping" value="cheese"> Extra Cheese </label></p>
  <p><label> <input type=checkbox name="topping" value="onion"> Onion </label></p>
  <p><label> <input type=checkbox name="topping" value="mushroom"> Mushroom </label></p>
 </fieldset>
 <p><label>Preferred delivery time: <input type=time min="11:00" max="21:00" step="900" name="delivery" required></label></p>
 <p><label>Delivery instructions: <textarea name="comments" maxlength=1000 inputmode="latin-prose"></textarea></label></p>
 <p><button>Submit order</button></p>
</form>

4.10.1.7 The difference between the field type, the autofill field name, and the input modality

This section is non-normative.

The type, autocomplete, and inputmode attributes can seem confusingly similar. For instance, in all three cases, the string "email" is a valid value. This section attempts to illustrate the difference between the three attributes and provides advice suggesting how to use them.

The type attribute on input elements decides what kind of control the user agent will use to expose the field. Choosing between different values of this attribute is the same choice as choosing whether to use an input element, a textarea element, a select element, a keygen element, etc.

The autocomplete attribute, in contrast, describes what the value that the user will enter actually represents. Choosing between different values of this attribute is the same choice as choosing what the label for the element will be.

First, consider telephone numbers. If a page is asking for a telephone number from the user, the right form control to use is <input type=tel>. However, which autocomplete value to use depends on which phone number the page is asking for, whether they expect a telephone number in the international format or just the local format, and so forth.

For example, a page that forms part of a checkout process on an e-commerce site for a customer buying a gift to be shipped to a friend might need both the buyer's telephone number (in case of payment issues) and the friend's telephone number (in case of delivery issues). If the site expects international phone numbers (with the country code prefix), this could thus look like this:

<p><label>Your phone number: <input type=tel name=custtel autocomplete="billing tel"></label>
<p><label>Recipient's phone number: <input type=tel name=shiptel autocomplete="shipping tel"></label>
<p>Please enter complete phone numbers including the country code prefix, as in "+1 555 123 4567".

But if the site only supports British customers and recipients, it might instead look like this (notice the use of tel-national rather than tel):

<p><label>Your phone number: <input type=tel name=custtel autocomplete="billing tel-national"></label>
<p><label>Recipient's phone number: <input type=tel name=shiptel autocomplete="shipping tel-national"></label>
<p>Please enter complete UK phone numbers, as in "(01632) 960 123".

Now, consider a person's preferred languages. The right autocomplete value is language. However, there could be a number of different form controls used for the purpose: a free text field (<input type=text>), a drop-down list (<select>), radio buttons (<input type=radio>), etc. It only depends on what kind of interface is desired.

The inputmode decides what kind of input modality (e.g. keyboard) to use, when the control is a free-form text field.

Consider names. If a page just wants one name from the user, then the relevant control is <input type=text>. If the page is asking for the user's full name, then the relevant autocomplete value is name. But if the user is Japanese, and the page is asking for the user's Japanese name and the user's romanised name, then it would be helpful to the user if the first field defaulted to a Japanese input modality, while the second defaulted to a Latin input modality (ideally with automatic capitalization of each word). This is where the inputmode attribute can help:

<p><label>Japanese name: <input name="j" type="text" autocomplete="section-jp name" inputmode="kana"></label>
<label>Romanised name: <input name="e" type="text" autocomplete="section-en name" inputmode="latin-name"></label>

In this example, the "section-*" keywords in the autocomplete attributes' values tell the user agent that the two fields expect different names. Without them, the user agent could automatically fill the second field with the value given in the first field when the user gave a value to the first field.

The "-jp" and "-en" parts of the keywords are opaque to the user agent; the user agent cannot guess, from those, that the two names are expected to be in Japanese and English respectively.

4.10.1.8 Date, time, and number formats

This section is non-normative.

In this pizza delivery example, the times are specified in the format "HH:MM": two digits for the hour, in 24-hour format, and two digits for the time. (Seconds could also be specified, though they are not necessary in this example.)

In some locales, however, times are often expressed differently when presented to users. For example, in the United States, it is still common to use the 12-hour clock with an am/pm indicator, as in "2pm". In France, it is common to separate the hours from the minutes using an "h" character, as in "14h00".

Similar issues exist with dates, with the added complication that even the order of the components is not always consistent — for example, in Cyprus the first of February 2003 would typically be written "1/2/03", while that same date in Japan would typically be written as "2003年02月01日" — and even with numbers, where locales differ, for example, in what punctuation is used as the decimal separator and the thousands separator.

It is therefore important to distinguish the time, date, and number formats used in HTML and in form submissions, which are always the formats defined in this specification (and based on the well-established ISO 8601 standard for computer-readable date and time formats), from the time, date, and number formats presented to the user by the browser and accepted as input from the user by the browser.

The format used "on the wire", i.e. in HTML markup and in form submissions, is intended to be computer-readable and consistent irrespective of the user's locale. Dates, for instance, are always written in the format "YYYY-MM-DD", as in "2003-02-01". Users are not expected to ever see this format.

The time, date, or number given by the page in the wire format is then translated to the user's preferred presentation (based on user preferences or on the locale of the page itself), before being displayed to the user. Similarly, after the user inputs a time, date, or number using their preferred format, the user agent converts it back to the wire format before putting it in the DOM or submitting it.

This allows scripts in pages and on servers to process times, dates, and numbers in a consistent manner without needing to support dozens of different formats, while still supporting the users' needs.

4.10.2 Categories

Mostly for historical reasons, elements in this section fall into several overlapping (but subtly different) categories in addition to the usual ones like flow content, phrasing content, and interactive content.

A number of the elements are form-associated elements, which means they can have a form owner.

• button
• fieldset
• input
• keygen
• label
• object
• output
• select
• textarea
• img

The form-associated elements fall into several subcategories:

Listed elements

Denotes elements that are listed in the form.elements and fieldset.elements APIs.

• button
• fieldset
• input
• keygen
• object
• output
• select
• textarea

Submittable elements

Denotes elements that can be used for constructing the form data set when a form element is submitted.

• button
• input
• keygen
• object
• select
• textarea

Some submittable elements can be, depending on their attributes, buttons. The prose below defines when an element is a button. Some buttons are specifically submit buttons.

Resettable elements

Denotes elements that can be affected when a form element is reset.

• input
• keygen
• output
• select
• textarea

Reassociateable elements

Denotes elements that have a form content attribute, and a matching form IDL attribute, that allow authors to specify an explicit form owner.

• button
• fieldset
• input
• keygen
• label
• object
• output
• select
• textarea

Some elements, not all of them form-associated, are categorised as labelable elements. These are elements that can be associated with a label element.

• button
• input (if the type attribute is not in the Hidden state)
• keygen
• meter
• output
• progress
• select
• textarea

4.10.3 The form element

Categories:

Flow content.

Palpable content.

Contexts in which this element can be used:

Where flow content is expected.

Content model:

Flow content, but with no form element descendants.

Content attributes:

Global attributes

accept-charset - Character encodings to use for form submission

action - URL to use for form submission

autocomplete - Default setting for autofill feature for controls in the form

enctype - Form data set encoding type to use for form submission

method - HTTP method to use for form submission

name - Name of form to use in the document.forms API

novalidate - Bypass form control validation for form submission

target - Browsing context for form submission

Tag omission in text/html:

Neither tag is omissible.

Allowed ARIA role attribute values:

Any role value.

Allowed ARIA state and property attributes:

Global aria-* attributes

Any aria-* attributes applicable to the allowed roles.

DOM interface:

[OverrideBuiltins]
interface HTMLFormElement : HTMLElement {
           attribute DOMString acceptCharset;
           attribute DOMString action;
           attribute DOMString autocomplete;
           attribute DOMString enctype;
           attribute DOMString encoding;
           attribute DOMString method;
           attribute DOMString name;
           attribute boolean noValidate;
           attribute DOMString target;

  readonly attribute HTMLFormControlsCollection elements;
  readonly attribute long length;
  getter Element (unsigned long index);
  getter (RadioNodeList or Element) (DOMString name);

  void submit();
  void reset();
  boolean checkValidity();
  boolean reportValidity();

  void requestAutocomplete();
};

The form element represents a collection of form-associated elements, some of which can represent editable values that can be submitted to a server for processing.

The accept-charset attribute gives the character encodings that are to be used for the submission. If specified, the value must be an ordered set of unique space-separated tokens that are ASCII case-insensitive, and each token must be an ASCII case-insensitive match for one of the labels of an ASCII-compatible character encoding. [ENCODING]

The name attribute represents the form's name within the forms collection. The value must not be the empty string, and the value must be unique amongst the form elements in the forms collection that it is in, if any.

The autocomplete attribute is an enumerated attribute. The attribute has two states. The on keyword maps to the on state, and the off keyword maps to the off state. The attribute may also be omitted. The missing value default is the on state. The off state indicates that by default, form controls in the form will have their autofill field name set to "off"; the on state indicates that by default, form controls in the form will have their autofill field name set to "on".

The action, enctype, method, novalidate, and target attributes are attributes for form submission.

form . elements

Returns an HTMLCollection of the form controls in the form (excluding image buttons for historical reasons).

form . length

Returns the number of form controls in the form (excluding image buttons for historical reasons).

form[index]

Returns the indexth element in the form (excluding image buttons for historical reasons).

form[name]

Returns the form control (or, if there are several, a RadioNodeList of the form controls) in the form with the given ID or name (excluding image buttons for historical reasons); or, if there are none, returns the img element with the given ID.

Once an element has been referenced using a particular name, that name will continue being available as a way to reference that element in this method, even if the element's actual ID or name changes, for as long as the element remains in the Document.

If there are multiple matching items, then a RadioNodeList object containing all those elements is returned.

form . submit()

Submits the form.

form . reset()

Resets the form.

form . checkValidity()

Returns true if the form's controls are all valid; otherwise, returns false.

form . reportValidity()

Returns true if the form's controls are all valid; otherwise, returns false and informs the user.

form . requestAutocomplete()

Triggers a user-agent-specific asynchronous user interface to help the user fill in any fields that have an autofill field name other than "on" or "off".

The form element will subsequently receive an event, either autocomplete, indicating that the fields have been prefilled, or autocompleteerror (using the AutocompleteErrorEvent interface), indicating that there was some problem (the general class of problem is described by the reason IDL attribute on the event).

<form action="http://www.google.com/search" method="get">
 <label>Google: <input type="search" name="q"></label> <input type="submit" value="Search...">
</form>
<form action="http://www.bing.com/search" method="get">
 <label>Bing: <input type="search" name="q"></label> <input type="submit" value="Search...">
</form>

4.10.4 The label element

Categories:

Flow content.

Phrasing content.

Interactive content.

Reassociateable form-associated element.

Palpable content.

Contexts in which this element can be used:

Where phrasing content is expected.

Content model:

Phrasing content, but with no descendant labelable elements unless it is the element's labeled control, and no descendant label elements.

Content attributes:

Global attributes

form - Associates the control with a form element

for - Associate the label with form control

Tag omission in text/html:

Neither tag is omissable

Allowed ARIA role attribute values:

None

Allowed ARIA state and property attributes:

Global aria-* attributes

DOM interface:

interface HTMLLabelElement : HTMLElement {
  readonly attribute HTMLFormElement? form;
           attribute DOMString htmlFor;
  readonly attribute HTMLElement? control;
};

The label element represents a caption in a user interface. The caption can be associated with a specific form control, known as the label element's labeled control, either using the for attribute, or by putting the form control inside the label element itself.

The for attribute may be specified to indicate a form control with which the caption is to be associated. If the attribute is specified, the attribute's value must be the ID of a labelable element in the same Document as the label element. If the attribute is specified and there is an element in the Document whose ID is equal to the value of the for attribute, and the first such element is a labelable element, then that element is the label element's labeled control.

<label><input type=checkbox name=lost> Lost</label>

  <!-- bad example - link inside label reduces checkbox activation area -->
  <label><input type=checkbox name=tac>I agree to <a href="tandc.html">the terms and conditions</a></label>

  
  <!-- bad example - all label text inside the link reduces activation area to checkbox only -->
  <label><input type=checkbox name=tac><a href="tandc.html">I agree to the terms and conditions</a></label>

 <!-- good example - link outside label means checkbox activation area includes the checkbox and all the label text -->
 <label><input type=checkbox name=tac>I agree to the terms and conditions</label>
(read <a href="tandc.html">Terms and Conditions</a>)
 

The form attribute is used to explicitly associate the label element with its form owner.

<p><label>Full name: <input name=fn> <small>Format: First Last</small></label></p>
<p><label>Age: <input name=age type=number min=0></label></p>
<p><label>Post code: <input name=pc> <small>Format: AB12 3CD</small></label></p>

label . control

Returns the form control that is associated with this element.

control . labels

Returns a NodeList of all the label elements that the form control is associated with.

4.10.5 The input element

Categories:

Flow content.

Phrasing content.

If the type attribute is not in the Hidden state: Interactive content.

If the type attribute is not in the Hidden state: Listed, labelable, submittable, resettable, and reassociateable form-associated element.

If the type attribute is in the Hidden state: Listed, submittable, resettable, and reassociateable form-associated element.

If the type attribute is not in the Hidden state: Palpable content.

Contexts in which this element can be used:

Where phrasing content is expected.

Content model:

Empty.

Content attributes:

Global attributes

accept - Hint for expected file type in file upload controls

alt - Replacement text for use when images are not available

autocomplete - Hint for form autofill feature

autofocus - Automatically focus the form control when the page is loaded

checked - Whether the command or control is checked

dirname - Name of form field to use for sending the element's directionality in form submission

disabled - Whether the form control is disabled

form - Associates the control with a form element

formaction - URL to use for form submission

formenctype - Form data set encoding type to use for form submission

formmethod - HTTP method to use for form submission

formnovalidate - Bypass form control validation for form submission

formtarget - Browsing context for form submission

height - Vertical dimension

inputmode - Hint for selecting an input modality

list - List of autocomplete options

max - Maximum value

maxlength - Maximum length of value

min - Minimum value

minlength - Minimum length of value

multiple - Whether to allow multiple values

name - Name of form control to use for form submission and in the form.elements API

pattern - Pattern to be matched by the form control's value

placeholder - User-visible label to be placed within the form control

readonly - Whether to allow the value to be edited by the user

required - Whether the control is required for form submission

size - Size of the control

src - Address of the resource

step - Granularity to be matched by the form control's value

type - Type of form control

value - Value of the form control

width - Horizontal dimension

Also, the title attribute has special semantics on this element when used in conjunction with the pattern attribute.

Tag omission in text/html:

No end tag

Allowed ARIA role attribute values:

Depends upon state of the type attribute.

Allowed ARIA state and property attributes:

Global aria-* attributes

Any aria-* attributes applicable to the allowed roles.

DOM interface:

interface HTMLInputElement : HTMLElement {
           attribute DOMString accept;
           attribute DOMString alt;
           attribute DOMString autocomplete;
           attribute boolean autofocus;
           attribute boolean defaultChecked;
           attribute boolean checked;
           attribute DOMString dirName;
           attribute boolean disabled;
  readonly attribute HTMLFormElement? form;
  readonly attribute FileList? files;
           attribute DOMString formAction;
           attribute DOMString formEnctype;
           attribute DOMString formMethod;
           attribute boolean formNoValidate;
           attribute DOMString formTarget;
           attribute unsigned long height;
           attribute boolean indeterminate;
           attribute DOMString inputMode;
  readonly attribute HTMLElement? list;
           attribute DOMString max;
           attribute long maxLength;
           attribute DOMString min;
           attribute long minLength;
           attribute boolean multiple;
           attribute DOMString name;
           attribute DOMString pattern;
           attribute DOMString placeholder;
           attribute boolean readOnly;
           attribute boolean required;
           attribute unsigned long size;
           attribute DOMString src;
           attribute DOMString step;
           attribute DOMString type;
           attribute DOMString defaultValue;
  [TreatNullAs=EmptyString] attribute DOMString value;
           attribute Date? valueAsDate;
           attribute unrestricted double valueAsNumber;
           attribute double valueLow;
           attribute double valueHigh;
           attribute unsigned long width;

  void stepUp(optional long n = 1);
  void stepDown(optional long n = 1);

  readonly attribute boolean willValidate;
  readonly attribute ValidityState validity;
  readonly attribute DOMString validationMessage;
  boolean checkValidity();
  boolean reportValidity();
  void setCustomValidity(DOMString error);

  readonly attribute NodeList labels;

  void select();
           attribute unsigned long selectionStart;
           attribute unsigned long selectionEnd;
           attribute DOMString selectionDirection;
  void setRangeText(DOMString replacement);
  void setRangeText(DOMString replacement, unsigned long start, unsigned long end, optional SelectionMode selectionMode = "preserve");
  void setSelectionRange(unsigned long start, unsigned long end, optional DOMString direction);
};

The input element represents a typed data field, usually with a form control to allow the user to edit the data.

The type attribute controls the data type (and associated control) of the element. It is an enumerated attribute. The following table lists the keywords and states for the attribute — the keywords in the left column map to the states in the cell in the second column on the same row as the keyword.

The missing value default is the Text state.

Which of the accept, alt, autocomplete, checked, dirname, formaction, formenctype, formmethod, formnovalidate, formtarget, height, inputmode, list, max, maxlength, min, minlength, multiple, pattern, placeholder, readonly, required, size, src, step, and width content attributes, the checked, files, valueAsDate, valueAsNumber, valueLow, valueHigh, and list IDL attributes, the select() method, the selectionStart, selectionEnd, and selectionDirection, IDL attributes, the setRangeText() and setSelectionRange() methods, the stepUp() and stepDown() methods, and the input and change events apply to an input element depends on the state of its type attribute. The subsections that define each type also clearly define in normative "bookkeeping" sections which of these feature apply, and which do not apply, to each type. The behavior of these features depends on whether they apply or not, as defined in their various sections (q.v. for content attributes, for APIs, for events).

The following table is non-normative and summarizes which of those content attributes, IDL attributes, methods, and events apply to each state:

* If the multiple attribute is not specified.

** If the multiple attribute is specified.

The value content attribute gives the default value of the input element. When the value content attribute is added, set, or removed, if the control's dirty value flag is false, the user agent must set the value of the element to the value of the value content attribute, if there is one, or the empty string otherwise, and then run the current value sanitization algorithm, if one is defined.

The checked content attribute is a boolean attribute that gives the default checkedness of the input element. When the checked content attribute is added, if the control does not have dirty checkedness, the user agent must set the checkedness of the element to true; when the checked content attribute is removed, if the control does not have dirty checkedness, the user agent must set the checkedness of the element to false.

The name attribute represents the element's name. The dirname attribute controls how the element's directionality is submitted. The disabled attribute is used to make the control non-interactive and to prevent its value from being submitted. The form attribute is used to explicitly associate the input element with its form owner. The autofocus attribute controls focus. The inputmode attribute controls the user interface's input modality for the control. The autocomplete attribute controls how the user agent provides autofill behavior.

4.10.5.1 States of the type attribute

4.10.5.1.1 Hidden state (type=hidden)

The input element represents a value that is not intended to be examined or manipulated by the user.

If the name attribute is present and has a value that is a case-sensitive match for the string "_charset_", then the element's value attribute must be omitted.

4.10.5.1.2 Text (type=text) state and Search state (type=search)

The input element represents a one line plain text edit control for the element's value.

The difference between the Text state and the Search state is primarily stylistic: on platforms where search fields are distinguished from regular text fields, the Search state might result in an appearance consistent with the platform's search fields rather than appearing like a regular text field.

The value attribute, if specified, must have a value that contains no "LF" (U+000A) or "CR" (U+000D) characters.

4.10.5.1.3 Telephone state (type=tel)

The input element represents a control for editing a telephone number given in the element's value.

The value attribute, if specified, must have a value that contains no "LF" (U+000A) or "CR" (U+000D) characters.

Unlike the URL and E-mail types, the Telephone type does not enforce a particular syntax. This is intentional; in practice, telephone number fields tend to be free-form fields, because there are a wide variety of valid phone numbers. Systems that need to enforce a particular format are encouraged to use the pattern attribute or the setCustomValidity() method to hook into the client-side validation mechanism.

4.10.5.1.4 URL state (type=url)

The input element represents a control for editing a single absolute URL given in the element's value.

The value attribute, if specified and not empty, must have a value that is a valid URL potentially surrounded by spaces that is also an absolute URL.

<input type="url" name="location" list="urls">
<datalist id="urls">
 <option label="MIME: Format of Internet Message Bodies" value="http://tools.ietf.org/html/rfc2045">
 <option label="HTML 4.01 Specification" value="http://www.w3.org/TR/html4/">
 <option label="Form Controls" value="http://www.w3.org/TR/xforms/slice8.html#ui-commonelems-hint">
 <option label="Scalable Vector Graphics (SVG) 1.1 Specification" value="http://www.w3.org/TR/SVG/">
 <option label="Feature Sets - SVG 1.1 - 20030114" value="http://www.w3.org/TR/SVG/feature.html">
 <option label="The Single UNIX Specification, Version 3" value="http://www.unix-systems.org/version3/">
</datalist>

4.10.5.1.5 E-mail state (type=email)

How the E-mail state operates depends on whether the multiple attribute is specified or not.

When the multiple attribute is not specified on the element

The input element represents a control for editing an e-mail address given in the element's value.

If the element is mutable, the user agent should allow the user to change the e-mail address represented by its value. User agents may allow the user to set the value to a string that is not a valid e-mail address. The user agent should act in a manner consistent with expecting the user to provide a single e-mail address. User agents should allow the user to set the value to the empty string. User agents must not allow users to insert "LF" (U+000A) or "CR" (U+000D) characters into the value. User agents may transform the value for display and editing; in particular, user agents should convert punycode in the value to IDN in the display and vice versa.

Constraint validation: While the user interface is representing input that the user agent cannot convert to punycode, the control is suffering from bad input.

The value attribute, if specified and not empty, must have a value that is a single valid e-mail address.

The value sanitization algorithm is as follows: Strip line breaks from the value, then strip leading and trailing whitespace from the value.

Constraint validation: While the value of the element is neither the empty string nor a single valid e-mail address, the element is suffering from a type mismatch.

When the multiple attribute is specified on the element

The input element represents a control for adding, removing, and editing the e-mail addresses given in the element's values.

If the element is mutable, the user agent should allow the user to add, remove, and edit the e-mail addresses represented by its values. User agents may allow the user to set any individual value in the list of values to a string that is not a valid e-mail address, but must not allow users to set any individual value to a string containing "," (U+002C), "LF" (U+000A), or "CR" (U+000D) characters. User agents should allow the user to remove all the addresses in the element's values. User agents may transform the values for display and editing; in particular, user agents should convert punycode in the value to IDN in the display and vice versa.

Constraint validation: While the user interface describes a situation where an individual value contains a "," (U+002C) or is representing input that the user agent cannot convert to punycode, the control is suffering from bad input.

Whenever the user changes the element's values, the user agent must run the following steps:

1. Let latest values be a copy of the element's values.

2. Strip leading and trailing whitespace from each value in latest values.

3. Let the element's value be the result of concatenating all the values in latest values, separating each value from the next by a single "," (U+002C) character, maintaining the list's order.

The value attribute, if specified, must have a value that is a valid e-mail address list.

The value sanitization algorithm is as follows:

1. Split on commas the element's value, strip leading and trailing whitespace from each resulting token, if any, and let the element's values be the (possibly empty) resulting list of (possibly empty) tokens, maintaining the original order.

2. Let the element's value be the result of concatenating the element's values, separating each value from the next by a single "," (U+002C) character, maintaining the list's order.

Constraint validation: While the value of the element is not a valid e-mail address list, the element is suffering from a type mismatch.

When the multiple attribute is set or removed, the user agent must run the value sanitization algorithm.

A valid e-mail address is a string that matches the email production of the following ABNF, the character set for which is Unicode. This ABNF implements the extensions described in RFC 1123. [ABNF] [RFC5322] [RFC1034] [RFC1123]

email         = 1*( atext / "." ) "@" label *( "." label )
label         = let-dig [ [ ldh-str ] let-dig ]  ; limited to a length of 63 characters by RFC 1034 section 3.5
atext         = < as defined in RFC 5322 section 3.2.3 >
let-dig       = < as defined in RFC 1034 section 3.5 >
ldh-str       = < as defined in RFC 1034 section 3.5 >

This requirement is a willful violation of RFC 5322, which defines a syntax for e-mail addresses that is simultaneously too strict (before the "@" character), too vague (after the "@" character), and too lax (allowing comments, whitespace characters, and quoted strings in manners unfamiliar to most users) to be of practical use here.

/^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$/

A valid e-mail address list is a set of comma-separated tokens, where each token is itself a valid e-mail address. To obtain the list of tokens from a valid e-mail address list, and implementation must split the string on commas.

4.10.5.1.6 Password state (type=password)

The input element represents a one line plain text edit control for the element's value. The user agent should obscure the value so that people other than the user cannot see it.

The value attribute, if specified, must have a value that contains no "LF" (U+000A) or "CR" (U+000D) characters.

4.10.5.1.7 Date and Time state (type=datetime)

The input element represents a control for setting the element's value to a string representing a specific global date and time. User agents may display the date and time in whatever time zone is appropriate for the user.

See the introduction section for a discussion of the difference between the input format and submission format for date, time, and number form controls, and the implementation notes regarding localization of form controls.

The value attribute, if specified and not empty, must have a value that is a valid global date and time string.

The min attribute, if specified, must have a value that is a valid global date and time string. The max attribute, if specified, must have a value that is a valid global date and time string.

The step attribute is expressed in seconds. The step scale factor is 1000 (which converts the seconds to milliseconds, as used in the other algorithms). The default step is 60 seconds.

<fieldset>
 <legend>Add Meeting</legend>
 <p><label>Meeting name: <input type=text name="meeting.label"></label>
 <p><label>Meeting time: <input type=datetime name="meeting.start"></label>
</fieldset>

4.10.5.1.8 Date state (type=date)

The input element represents a control for setting the element's value to a string representing a specific date.

date values represent a "floating" time and do not include time zone information. Care is needed when converting values of this type to or from date data types in JavaScript and other programming languages. In many cases, an implicit time-of-day and time zone are used to create a global ("incremental") time (an integer value that represents the offset from some arbitrary epoch time). Processing or conversion of these values, particularly across time zones, can change the value of the date itself. [TIMEZONES]

See the introduction section for a discussion of the difference between the input format and submission format for date, time, and number form controls, and the implementation notes regarding localization of form controls.

The value attribute, if specified and not empty, must have a value that is a valid date string.

The min attribute, if specified, must have a value that is a valid date string. The max attribute, if specified, must have a value that is a valid date string.

The step attribute is expressed in days. The step scale factor is 86,400,000 (which converts the days to milliseconds, as used in the other algorithms). The default step is 1 day.

See the note on historical dates in the Date and Time state section.

4.10.5.1.9 Month state (type=month)

The input element represents a control for setting the element's value to a string representing a specific month.

See the introduction section for a discussion of the difference between the input format and submission format for date, time, and number form controls, and the implementation notes regarding localization of form controls.

The value attribute, if specified and not empty, must have a value that is a valid month string.

The min attribute, if specified, must have a value that is a valid month string. The max attribute, if specified, must have a value that is a valid month string.

The step attribute is expressed in months. The step scale factor is 1 (there is no conversion needed as the algorithms use months). The default step is 1 month.

4.10.5.1.10 Week state (type=week)

The input element represents a control for setting the element's value to a string representing a specific week.

See the introduction section for a discussion of the difference between the input format and submission format for date, time, and number form controls, and the implementation notes regarding localization of form controls.

The value attribute, if specified and not empty, must have a value that is a valid week string.

The min attribute, if specified, must have a value that is a valid week string. The max attribute, if specified, must have a value that is a valid week string.

The step attribute is expressed in weeks. The step scale factor is 604,800,000 (which converts the weeks to milliseconds, as used in the other algorithms). The default step is 1 week. The default step base is −259,200,000 (the start of week 1970-W01).

4.10.5.1.11 Time state (type=time)

The input element represents a control for setting the element's value to a string representing a specific time.

See the introduction section for a discussion of the difference between the input format and submission format for date, time, and number form controls, and the implementation notes regarding localization of form controls.

The value attribute, if specified and not empty, must have a value that is a valid time string.

The min attribute, if specified, must have a value that is a valid time string. The max attribute, if specified, must have a value that is a valid time string.

The step attribute is expressed in seconds. The step scale factor is 1000 (which converts the seconds to milliseconds, as used in the other algorithms). The default step is 60 seconds.

4.10.5.1.12 Number state (type=number)

The input element represents a control for setting the element's value to a string representing a number.

This specification does not define what user interface user agents are to use; user agent vendors are encouraged to consider what would best serve their users' needs. For example, a user agent in Persian or Arabic markets might support Persian and Arabic numeric input (converting it to the format required for submission as described above). Similarly, a user agent designed for Romans might display the value in Roman numerals rather than in decimal; or (more realistically) a user agent designed for the French market might display the value with apostrophes between thousands and commas before the decimals, and allow the user to enter a value in that manner, internally converting it to the submission format described above.

The value attribute, if specified and not empty, must have a value that is a valid floating-point number.

The min attribute, if specified, must have a value that is a valid floating-point number. The max attribute, if specified, must have a value that is a valid floating-point number.

The step scale factor is 1. The default step is 1 (allowing only integers to be selected by the user, unless the step base has a non-integer value).

<label>How much do you want to charge? $<input type=number min=0 step=0.01 name=price></label>

The type=number state is not appropriate for input that happens to only consist of numbers but isn't strictly speaking a number. For example, it would be inappropriate for credit card numbers or US postal codes. A simple way of determining whether to use type=number is to consider whether it would make sense for the input control to have a spinbox interface (e.g. with "up" and "down" arrows). Getting a credit card number wrong by 1 in the last digit isn't a minor mistake, it's as wrong as getting every digit incorrect. So it would not make sense for the user to select a credit card number using "up" and "down" buttons. When a spinbox interface is not appropriate, type=text is probably the right choice (possibly with a pattern attribute).

4.10.5.1.13 Range state (type=range)

How the Range state operates depends on whether the multiple attribute is specified or not.

When the multiple attribute is not specified on the element

The input element represents a control for setting the element's value to a string representing a number, but with the caveat that the exact value is not important, letting UAs provide a simpler interface than they do for the Number state.

If the element is mutable, the user agent should allow the user to change the number represented by its value, as obtained from applying the rules for parsing floating-point number values to it. User agents must not allow the user to set the value to a string that is not a valid floating-point number. If the user agent provides a user interface for selecting a number, then the value must be set to a best representation of the number representing the user's selection as a floating-point number. User agents must not allow the user to set the value to the empty string.

Constraint validation: While the user interface describes input that the user agent cannot convert to a valid floating-point number, the control is suffering from bad input.

The value attribute, if specified, must have a value that is a valid floating-point number.

The value sanitization algorithm is as follows: If the value of the element is not a valid floating-point number, then set it to the best representation, as a floating-point number, of the default value.

The default value is the minimum plus half the difference between the minimum and the maximum, unless the maximum is less than the minimum, in which case the default value is the minimum.

When the element is suffering from an underflow, the user agent must set the element's value to the best representation, as a floating-point number, of the minimum.

When the element is suffering from an overflow, if the maximum is not less than the minimum, the user agent must set the element's value to a valid floating-point number that represents the maximum.

When the element is suffering from a step mismatch, the user agent must round the element's value to the nearest number for which the element would not suffer from a step mismatch, and which is greater than or equal to the minimum, and, if the maximum is not less than the minimum, which is less than or equal to the maximum, if there is a number that matches these constraints. If two numbers match these constraints, then user agents must use the one nearest to positive infinity.

For example, the markup <input type="range" min=0 max=100 step=20 value=50> results in a range control whose initial value is 60.

Here is an example of a range control using an autocomplete list with the list attribute. This could be useful if there are values along the full range of the control that are especially important, such as preconfigured light levels or typical speed limits in a range control used as a speed control. The following markup fragment:

<input type="range" min="-100" max="100" value="0" step="10" name="power" list="powers">
<datalist id="powers">
 <option value="0">
 <option value="-30">
 <option value="30">
 <option value="++50">
</datalist>

...with the following style sheet applied:

input { height: 75px; width: 49px; background: #D5CCBB; color: black; }

...might render as:

Note how the UA determined the orientation of the control from the ratio of the style-sheet-specified height and width properties. The colors were similarly derived from the style sheet. The tick marks, however, were derived from the markup. In particular, the step attribute has not affected the placement of tick marks, the UA deciding to only use the author-specified completion values and then adding longer tick marks at the extremes.

Note also how the invalid value ++50 was completely ignored.

For another example, consider the following markup fragment:

<input name=x type=range min=100 max=700 step=9.09090909 value=509.090909>

A user agent could display in a variety of ways, for instance:

Or, alternatively, for instance:

The user agent could pick which one to display based on the dimensions given in the style sheet. This would allow it to maintain the same resolution for the tick marks, despite the differences in width.

Finally, here is an example of a range control with two labeled values:

<input type="range" name="a" list="a-values">
<datalist id="a-values">
 <option value="10" label="Low">
 <option value="90" label="High">
</datalist>

With styles that make the control draw vertically, it might look as follows:

When the multiple attribute is specified on the element

The input element represents a control for setting the element's values to two strings representing numbers, but with the caveat that the exact values are not important, enabling UAs provide a graphical interface rather than requiring the user to type the numbers directly.

If the element is mutable, the user agent should allow the user to change either the first or second number represented by its values, as obtained from applying the rules for parsing floating-point number values to them, and ensuring that the first value is never larger than the second value. User agents must not allow the user to set either the first or second of the values to a string that is not a valid floating-point number. If the user agent provides a user interface for selecting a number, then these values must be set to the best representations of the numbers representing the user's selections as floating-point numbers. User agents must not allow the user to set the values to the empty string.

Constraint validation: While the user interface describes input that the user agent cannot convert to a pair of valid floating-point numbers, the control is suffering from bad input.

The value attribute, if specified, must have a value that is a pair of valid floating-point numbers separated by a single "," (U+002C) character.

The value sanitization algorithm is as follows:

1. Split on commas the element's value.

2. If there are not exactly two values, or if either value is not a valid floating-point number, then let the element's values be a pair of values consisting of a best representation, as a floating-point number, of the element's minimum and the element's maximum, with the smaller value first.

3. Othwerwise, let the element's values be the two values, with the smaller value first.

4. Let the element's value be the result of concatenating the element's values, separating them by a single "," (U+002C) character, with the lower value coming first.

Whenever the user changes the element's values, the user agent must set the element's value to the result of concatenating the element's values, separating them by a single "," (U+002C) character, with the lower value coming first.

When the element is suffering from an underflow, the user agent must set either of the element's values that represent values less than the minimum to the best representation, as a floating-point number, of the minimum.

When the element is suffering from an overflow, if the maximum is not less than the minimum, the user agent must set either of the element's values that represent values greater than the maximum to a valid floating-point number that represents the maximum.

When the element is suffering from a step mismatch, the user agent must round the values represented by the element's values to, in each case, the nearest number for which the element would not suffer from a step mismatch, and which is greater than or equal to the minimum, and, if the maximum is not less than the minimum, which is less than or equal to the maximum, if there is a number that matches these constraints. If two numbers match these constraints, then user agents must use the one nearest to positive infinity.

Whenever the user agent changes the element's values according to the three previous paragraphs, the user agent must set the element's value to the result of concatenating the element's values, separating them by a single U+002C COMMA character (,), with the lower value coming first.

Consider a user interface that filters possible flights by departure and arrival time:

<form ...>
 <fieldset>
  <legend>Outbound flight time</legend>
  <select ...>
   <option>Departure
   <option>Arrival
  </select>
  <p><output name=o1>00:00</output> – <output name=o2>24:00</output></p>
  <input type=range multiple min=0 max=24 value=0,24 step=1.0 ...
         oninput="o1.value = valueLow + ':00'; o2.value = valueHigh + ':00'">
 </fieldset>
 ...
</form>

With appropriate styling, this might look like:

When the multiple attribute is set or removed, the user agent must run the value sanitization algorithm.

In this state, the range and step constraints are enforced even during user input, and there is no way to set the value to the empty string.

The min attribute, if specified, must have a value that is a valid floating-point number. The default minimum is 0. The max attribute, if specified, must have a value that is a valid floating-point number. The default maximum is 100.

The step scale factor is 1. The default step is 1 (allowing only integers, unless the min attribute has a non-integer value).

4.10.5.1.14 Color state (type=color)

The input element represents a color well control, for setting the element's value to a string representing a simple color.

The value attribute, if specified and not empty, must have a value that is a valid simple color.

4.10.5.1.15 Checkbox state (type=checkbox)

The input element represents a two-state control that represents the element's checkedness state. If the element's checkedness state is true, the control represents a positive selection, and if it is false, a negative selection. If the element's indeterminate IDL attribute is set to true, then the control's selection should be obscured as if the control was in a third, indeterminate, state.

The control is never a true tri-state control, even if the element's indeterminate IDL attribute is set to true. The indeterminate IDL attribute only gives the appearance of a third state.

input . indeterminate [ = value ]

When set, overrides the rendering of checkbox controls so that the current value is not visible.

4.10.5.1.16 Radio Button state (type=radio)

The input element represents a control that, when used in conjunction with other input elements, forms a radio button group in which only one control can have its checkedness state set to true. If the element's checkedness state is true, the control represents the selected control in the group, and if it is false, it indicates a control in the group that is not selected.

The radio button group that contains an input element a also contains all the other input elements b that fulfill all of the following conditions:

• The input element b's type attribute is in the Radio Button state.
• Either a and b have the same form owner, or they both have no form owner.
• Both a and b are in the same home subtree.
• They both have a name attribute, their name attributes are not empty, and the value of a's name attribute is a compatibility caseless match for the value of b's name attribute.

A document must not contain an input element whose radio button group contains only that element.

If none of the radio buttons in a radio button group are checked when they are inserted into the document, then they will all be initially unchecked in the interface, until such time as one of them is checked (either by the user or by script).

4.10.5.1.17 File Upload state (type=file)

The input element represents a list of selected files, each file consisting of a file name, a file type, and a file body (the contents of the file).

The accept attribute may be specified to provide user agents with a hint of what file types will be accepted.

If specified, the attribute must consist of a set of comma-separated tokens, each of which must be an ASCII case-insensitive match for one of the following:

The string audio/*

Indicates that sound files are accepted.

The string video/*

Indicates that video files are accepted.

The string image/*

Indicates that image files are accepted.

A valid MIME type with no parameters

Indicates that files of the specified type are accepted.

A string whose first character is a "." (U+002E) character

Indicates that files with the specified file extension are accepted.

The tokens must not be ASCII case-insensitive matches for any of the other tokens (i.e. duplicates are not allowed). To obtain the list of tokens from the attribute, the user agent must split the attribute value on commas.

User agents may use the value of this attribute to display a more appropriate user interface than a generic file picker. For instance, given the value image/*, a user agent could offer the user the option of using a local camera or selecting a photograph from their photo collection; given the value audio/*, a user agent could offer the user the option of recording a clip using a headset microphone.

Authors are encouraged to specify both any MIME types and any corresponding extensions when looking for data in a specific format.

<input type="file" accept=".doc,.docx,.xml,application/msword,application/vnd.openxmlformats-officedocument.wordprocessingml.document">

Extensions tend to be ambiguous (e.g. there are an untold number of formats that use the ".dat" extension, and users can typically quite easily rename their files to have a ".doc" extension even if they are not Microsoft Word documents), and MIME types tend to be unreliable (e.g. many formats have no formally registered types, and many formats are in practice labeled using a number of different MIME types). Authors are reminded that, as usual, data received from a client should be treated with caution, as it may not be in an expected format even if the user is not hostile and the user agent fully obeyed the accept attribute's requirements.

function extractFilename(path) {
  if (path.substr(0, 12) == "C:\\fakepath\\")
    return path.substr(12); // modern browser
  var x;
  x = path.lastIndexOf('/');
  if (x >= 0) // Unix-based path
    return path.substr(x+1);
  x = path.lastIndexOf('\\');
  if (x >= 0) // Windows-based path
    return path.substr(x+1);
  return path; // just the file name
}

<p><input type=file name=image onchange="updateFilename(this.value)"></p>
<p>The name of the file you picked is: <span id="filename">(none)</span></p>
<script>
 function updateFilename(path) {
   var name = extractFilename(path);
   document.getElementById('filename').textContent = name;
 }
</script>

4.10.5.1.18 Submit Button state (type=submit)

The input element represents a button that, when activated, submits the form. If the element has a value attribute, the button's label must be the value of that attribute; otherwise, it must be an implementation-defined string that means "Submit" or some such. The element is a button, specifically a submit button.

The formaction, formenctype, formmethod, formnovalidate, and formtarget attributes are attributes for form submission.

The formnovalidate attribute can be used to make submit buttons that do not trigger the constraint validation.

4.10.5.1.19 Image Button state (type=image)

The input element represents either an image from which a user can select a coordinate and submit the form, or alternatively a button from which the user can submit the form. The element is a button, specifically a submit button.

The coordinate is sent to the server during form submission by sending two entries for the element, derived from the name of the control but with ".x" and ".y" appended to the name with the x and y components of the coordinate respectively.

The image is given by the src attribute. The src attribute must be present, and must contain a valid non-empty URL potentially surrounded by spaces referencing a non-interactive, optionally animated, image resource that is neither paged nor scripted.

The alt attribute provides the textual label for the button for users and user agents who cannot use the image. The alt attribute must be present, and must contain a non-empty string giving the label that would be appropriate for an equivalent button if the image was unavailable.

The input element supports dimension attributes.

The formaction, formenctype, formmethod, formnovalidate, and formtarget attributes are attributes for form submission.

image . width [ = value ]

image . height [ = value ]

These attributes return the actual rendered dimensions of the image, or zero if the dimensions are not known.

They can be set, to change the corresponding content attributes.

Many aspects of this state's behavior are similar to the behavior of the img element. Readers are encouraged to read that section, where many of the same requirements are described in more detail.

<form action="process.cgi">
 <input type=image src=map.png name=where alt="Show location list">
</form>

4.10.5.1.20 Reset Button state (type=reset)

The input element represents a button that, when activated, resets the form. If the element has a value attribute, the button's label must be the value of that attribute; otherwise, it must be an implementation-defined string that means "Reset" or some such. The element is a button.

4.10.5.1.21 Button state (type=button)

The input element represents a button with no default behavior. A label for the button must be provided in the value attribute, though it may be the empty string. If the element has a value attribute, the button's label must be the value of that attribute; otherwise, it must be the empty string. The element is a button.

4.10.5.3 Common input element attributes

4.10.5.3.1 The maxlength and minlength attributes

The maxlength attribute, when it applies, is a form control maxlength attribute controlled by the input element's dirty value flag.

The minlength attribute, when it applies, is a form control minlength attribute controlled by the input element's dirty value flag.

If the input element has a maximum allowed value length, then the code-unit length of the value of the element's value attribute must be equal to or less than the element's maximum allowed value length.

<label>What are you doing? <input name=status maxlength=140></label>

<p><label>Username: <input name=u required></label>
<p><label>Password: <input name=p required minlength=12></label>

4.10.5.3.2 The size attribute

The size attribute gives the number of characters that, in a visual rendering, the user agent is to allow the user to see while editing the element's value.

The size attribute, if specified, must have a value that is a valid non-negative integer greater than zero.

4.10.5.3.3 The readonly attribute

The readonly attribute is a boolean attribute that controls whether or not the user can edit the form control. When specified, the element is not mutable.

The difference between disabled and readonly is that read-only controls are still focusable, so the user can still select the text and interact with it, whereas disabled controls are entirely non-interactive. (For this reason, only text controls can be made read-only: it wouldn't make sense for checkboxes or buttons, for instances.)

<form action="products.cgi" method="post" enctype="multipart/form-data">
 <table>
  <tr> <th> Product ID <th> Product name <th> Price <th> Action
  <tr>
   <td> <input readonly="readonly" name="1.pid" value="H412">
   <td> <input required="required" name="1.pname" value="Floor lamp Ulke">
   <td> $<input required="required" type="number" min="0" step="0.01" name="1.pprice" value="49.99">
   <td> <button formnovalidate="formnovalidate" name="action" value="delete:1">Delete</button>
  <tr>
   <td> <input readonly="readonly" name="2.pid" value="FG28">
   <td> <input required="required" name="2.pname" value="Table lamp Ulke">
   <td> $<input required="required" type="number" min="0" step="0.01" name="2.pprice" value="24.99">
   <td> <button formnovalidate="formnovalidate" name="action" value="delete:2">Delete</button>
  <tr>
   <td> <input required="required" name="3.pid" value="" pattern="[A-Z0-9]+">
   <td> <input required="required" name="3.pname" value="">
   <td> $<input required="required" type="number" min="0" step="0.01" name="3.pprice" value="">
   <td> <button formnovalidate="formnovalidate" name="action" value="delete:3">Delete</button>
 </table>
 <p> <button formnovalidate="formnovalidate" name="action" value="add">Add</button> </p>
 <p> <button name="action" value="update">Save</button> </p>
</form>

4.10.5.3.4 The required attribute

The required attribute is a boolean attribute. When specified, the element is required.

<h1>Create new account</h1>
<form action="/newaccount" method=post
      oninput="up2.setCustomValidity(up2.value != up.value ? 'Passwords do not match.' : '')">
 <p>
  <label for="username">E-mail address:</label>
  <input id="username" type=email required name=un>
 <p>
  <label for="password1">Password:</label>
  <input id="password1" type=password required name=up>
 <p>
  <label for="password2">Confirm password:</label>
  <input id="password2" type=password name=up2>
 <p>
  <input type=submit value="Create account">
</form>

<fieldset>
 <legend>Did the movie pass the Bechdel test?</legend>
 <p><label><input type="radio" name="bechdel" value="no-characters"> No, there are not even two female characters in the movie. </label>
 <p><label><input type="radio" name="bechdel" value="no-names"> No, the female characters never talk to each other. </label>
 <p><label><input type="radio" name="bechdel" value="no-topic"> No, when female characters talk to each other it's always about a male character. </label>
 <p><label><input type="radio" name="bechdel" value="yes" required> Yes. </label>
 <p><label><input type="radio" name="bechdel" value="unknown"> I don't know. </label>
</fieldset>

4.10.5.3.5 The multiple attribute

The multiple attribute is a boolean attribute that indicates whether the user is to be allowed to specify more than one value.

<label>Cc: <input type=email multiple name=cc></label>

<label>Cc: <input type=email multiple name=cc list=contacts></label>
...
<datalist id="contacts">
 <option value="hedral@damowmow.com">
 <option value="pillar@example.com">
 <option value="astrophy@cute.example">
 <option value="astronomy@science.example.org">
</datalist>

<label>Attachments: <input type=file multiple name=att></label>

4.10.5.3.6 The pattern attribute

The pattern attribute specifies a regular expression against which the control's value, or, when the multiple attribute applies and is set, the control's values, are to be checked.

If specified, the attribute's value must match the JavaScript Pattern production. [ECMA262]

When an input element has a pattern attribute specified, authors should provide a description of the pattern in text near the control. Authors may also include a title attribute to give a description of the pattern. User agents may use the contents of this attribute, if it is present, when informing the user that the pattern is not matched, or at any other suitable time, such as in a tooltip or read out by assistive technology when the control gains focus.

Relying on the title attribute alone is currently discouraged as many user agents do not expose the attribute in an accessible manner as required by this specification (e.g. requiring a pointing device such as a mouse to cause a tooltip to appear, which excludes keyboard-only users and touch-only users, such as anyone with a modern phone or tablet).

<label> Part number:
        <input pattern="[0-9][A-Z]{3}" name="part"
        data-x="A part number is a digit followed by three uppercase letters."/>
        </label>
        <p>A part number is a digit followed by three uppercase letters.</p>

A part number is a digit followed by three uppercase letters.
    You cannot submit this form when the field is incorrect.

<label> Part number:
        <input pattern="[0-9][A-Z]{3}" name="part" aria-describedby="description">
        </label>
        <p id="description">A part number is a digit followed by three uppercase letters.</p>

When a control has a pattern attribute, the title attribute, if used, must describe the pattern. Additional information could also be included, so long as it assists the user in filling in the control. Otherwise, assistive technology would be impaired.

For instance, if the title attribute contained the caption of the control, assistive technology could end up saying something like The text you have entered does not match the required pattern. Birthday, which is not useful.

UAs may still show the title in non-error situations (for example, as a tooltip when hovering over the control), so authors should be careful not to word titles as if an error has necessarily occurred.

4.10.5.3.7 The min and max attributes

Some form controls can have explicit constraints applied limiting the allowed range of values that the user can provide. Normally, such a range would be linear and continuous. A form control can have a periodic domain, however, in which case the form control's broadest possible range is finite, and authors can specify explicit ranges within it that span the boundaries.

Specifically, the broadest range of a type=time control is midnight to midnight (24 hours), and authors can set both continuous linear ranges (such as 9pm to 11pm) and discontinuous ranges spanning midnight (such as 11pm to 1am).

The min and max attributes indicate the allowed range of values for the element.

If the element does not have a periodic domain, the max attribute's value (the maximum) must not be less than the min attribute's value (its minimum).

An element has range limitations if it has a defined minimum or a defined maximum.

<input name=bday type=date max="1979-12-31">

<input name=quantity required="" type="number" min="1" value="1">

<input name="sleepStart" type=time min="21:00" max="06:00" step="60" value="00:00">

4.10.5.3.8 The step attribute

The step attribute indicates the granularity that is expected (and required) of the value or values, by limiting the allowed values. The section that defines the type attribute's current state also defines the default step, the step scale factor, and in some cases the default step base, which are used in processing the attribute as described below.

The step attribute, if specified, must either have a value that is a valid floating-point number that parses to a number that is greater than zero, or must have a value that is an ASCII case-insensitive match for the string "any".