Allows a form field to be immediately focused on page load.
contenteditable attribute (basic support)
Method of making any HTML element editable.
Case-insensitive CSS attribute selectors
Including an `i` before the `]` in a CSS attribute selector causes the attribute value to be matched in an ASCII-case-insensitive manner. For example, `[b="xyz" i]` would match both `<a b="xyz">` and `<a b="XYZ">`.
CSS3 attr() function for all properties
While `attr()` is supported for effectively all browsers for the `content` property, CSS Values and Units Level 3 adds the ability to use `attr()` on **any** CSS property, and to use it for non-string values (e.g. numbers, colors).
dataset & data-* attributes
Method of applying and accessing custom data to elements.
When used on an anchor, this attribute signifies that the browser should download the resource the anchor points to rather than navigate to it.
disabled attribute of the fieldset element
Allows disabling all of the form control descendants of a fieldset via a `disabled` attribute on the fieldset element itself.
Attribute for associating input and submit buttons with a form.
Attributes for form submission
Attributes for form submission that may be specified on submit buttons. The attributes are: `formaction`, `formenctype`, `formmethod`, `formnovalidate`, and `formtarget`
The `hidden` attribute may be applied to any element, and effectively hides elements similar to `display: none` in CSS.
sandbox attribute for iframes
seamless attribute for iframes
The seamless attribute makes an iframe's contents actually part of a page, and adopts the styles from its hosting page. The attribute has been removed from both [the WHATWG](https://github.com/whatwg/html/issues/331) and [the W3C](https://github.com/w3c/html/pull/325) HTML5 specifications.
srcdoc attribute for iframes
Override the content specified in the `src` attribute (if present) with HTML content within the attribute.
autocomplete attribute: on & off values
The `autocomplete` attribute for `input` elements indicates to the browser whether a value should or should not be autofilled when appropriate.
accept attribute for file input
Allows a filter to be defined for what type of files a user may pick with from an `<input type="file">` dialog
The `inputmode` attribute specifies what kind of input mechanism would be most helpful for users entering content into the form control.
Minimum length attribute for input fields
Declares a lower bound on the number of characters a user can input.
Pattern attribute for input fields
Allows validation of an input field based on a given regular expression pattern.
input placeholder attribute
Method of setting placeholder text for text-like input fields, to suggest the expected inserted information.
Lazy loading via attribute for images & iframes
The `loading` attribute on images & iframes gives authors control over when the browser should start loading the resource.
maxlength attribute for input and textarea elements
Declares an upper bound on the number of characters the user can input. Normally the UI ignores attempts by the user to type in additional characters beyond this limit.
Reversed attribute of ordered lists
This attribute makes an ordered list number its items in descending order (large to small), instead of ascending order (small to large; the default). The order that the list items are displayed in is not affected.
When used on an anchor, this attribute signifies that the browser should send a ping request the resource the attribute points to.
readonly attribute of input and textarea elements
Makes the form control non-editable. Unlike the `disabled` attribute, `readonly` form controls are still included in form submissions and the user can still select (but not edit) their value text.
'SameSite' cookie attribute
Same-site cookies ("First-Party-Only" or "First-Party") allow servers to mitigate the risk of CSRF and information leakage attacks by asserting that a particular cookie should only be sent with requests initiated from the same registrable domain.
async attribute for external scripts
defer attribute for external scripts
Attribute for `input`/`textarea` fields to enable/disable the browser's spellchecker.
Srcset and sizes attributes
The `srcset` and `sizes` attributes on `img` (or `source`) elements allow authors to define various image resources and "hints" that assist a user agent to determine the most appropriate image source to display (e.g. high-resolution displays, small monitors, etc).
tabindex global attribute
Specifies the focusability of the element and in what order (if any) it should become focused (relative to other elements) when "tabbing" through the document.
attr api: localname
attr api: name
attr api: namespaceuri
attr api: ownerelement
attr api: prefix
attr api: specified
attr api: value
attributes: core: id
attributes: core: tabindex
attributes: core: xml:space
attributes: presentation: letter-spacing
attributes: presentation: paint-order
attributes: presentation: word-spacing
attributes: style: class
attributes: style: style