The modern standard API for adding DOM event handlers. Introduced in the DOM Level 2 Events spec. Also implies support for `removeEventListener`, the [capture phase](https://dom.spec.whatwg.org/#dom-event-capturing_phase) of DOM event dispatch, as well as the `stopPropagation()` and `preventDefault()` event methods.
HEVC/H.265 video format
The High Efficiency Video Coding (HEVC) compression standard is a video compression format intended to succeed H.264. It is hard for browsers to universally support HEVC because it is [complex and expensive to license](https://en.wikipedia.org/wiki/High_Efficiency_Video_Coding#Patent_licensing). HEVC competes with [AV1](/av1) which has similar compression quality and provides a free license.
Networking protocol for low-latency transport of content over the web. Originally started out from the SPDY protocol, now standardized as HTTP version 2.
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.
Context menu item (menuitem element)
Method of defining a context menu item, now deprecated and [removed from the HTML specification](https://github.com/whatwg/html/issues/2730).
Networking protocol for low-latency transport of content over the web. Superseded by HTTP version 2.
Deprecated method of allowing scoped CSS styles using a "scoped" attribute. Now [removed from the specification](https://github.com/whatwg/html/issues/552) and replaced by the [@scope CSS rule](/css-cascade-scope).
Method of using fonts defined as SVG shapes. Removed from [SVG 2.0](https://www.w3.org/TR/SVG2/changes.html#fonts) and considered as a deprecated feature with support being removed from browsers.
XMLHttpRequest advanced features
Adds more functionality to XHR (aka AJAX) requests like file uploads, transfer progress information and the ability to send form data. Previously known as [XMLHttpRequest Level 2](https://www.w3.org/TR/2012/WD-XMLHttpRequest-20120117/), these features now appear simply in the XMLHttpRequest spec.
headers http header: authorization: `digest` authentication: sha2-256 digest authentication
headers http header: authorization: `digest` authentication: sha2-512 digest authentication
headers http header: www-authenticate: `digest` authentication: sha2-256 digest authentication
headers http header: www-authenticate: `digest` authentication: sha2-512 digest authentication
http status code: 200
http status code: 201
http status code: 204
http status code: 206
http status code: 302
http status code: 412
http status code: 425
http status code: 502