Background Sync API

Provides one-off and periodic synchronization for Service Workers with an onsync event.

Content Security Policy 1.0

Mitigate cross-site scripting attacks by only allowing certain sources of script, style, and other resources.

Content Security Policy Level 2

Mitigate cross-site scripting attacks by only allowing certain sources of script, style, and other resources. CSP 2 adds hash-source, nonce-source, and five new directives

Cookie Store API

An API for reading and modifying cookies. Compared to the existing `document.cookie` method, the API provides a much more modern interface, which can also be used in service workers.

CSS Filter Effects

Method of applying filter effects using the `filter` property to elements, matching filters available in SVG. Filter functions include blur, brightness, contrast, drop-shadow, grayscale, hue-rotate, invert, opacity, sepia and saturate.

CSS 2.1 selectors

Basic CSS selectors including: `*` (universal selector), `>` (child selector), `:first-child`, `:link`, `:visited`, `:active`, `:hover`, `:focus`, `:lang()`, `+` (adjacent sibling selector), `[attr]`, `[attr="val"]`, `[attr~="val"]`, `[attr|="bar"]`, `.foo` (class selector), `#foo` (id selector)

ECMAScript 2015 (ES6)

Support for the ECMAScript 2015 specification. Features include Promises, Modules, Classes, Template Literals, Arrow Functions, Let and Const, Default Parameters, Generators, Destructuring Assignment, Rest & Spread, Map/Set & WeakMap/WeakSet and many more.

CSS Flexible Box Layout Module

Method of positioning elements in horizontal or vertical stacks. Support includes all properties prefixed with `flex`, as well as `display: flex`, `display: inline-flex`, `align-content`, `align-items`, `align-self`, `justify-content` and `order`.

Search input type

Search field form input type. Intended to look like the underlying platform's native search field widget (if there is one). Other than its appearance, it's the same as an `<input type="text">`.

Screen Orientation

Provides the ability to read the screen orientation state, to be informed when this state changes, and to be able to lock the screen orientation to a specific state.

scrollIntoView

The `Element.scrollIntoView()` method scrolls the current element into the visible area of the browser window. Parameters can be provided to set the position inside the visible area as well as whether scrolling should be instant or smooth.

Element.scrollIntoViewIfNeeded()

If the element is fully within the visible area of the viewport, it does nothing. Otherwise, the element is scrolled into view. A proprietary variant of the standard `Element.scrollIntoView()` method.

SDCH Accept-Encoding/Content-Encoding

Shared Dictionary Compression over HTTP

Selection API

API for accessing selected content of a document, including the `window.getSelection()` method, as well as the `selectstart` & `selectionchange` events on `document`.

Server Timing

Mechanism for web developers to annotate network requests with server timing information.

Efficient Script Yielding: setImmediate()

Yields control flow without the minimum delays enforced by setTimeout

Shadow DOM (deprecated V0 spec)

Original V0 version of the Shadow DOM specification. See [Shadow DOM V1](#feat=shadowdomv1) for support for the latest version.

Shadow DOM (V1)

Method of establishing and maintaining functional boundaries between DOM trees and how these trees interact with each other within a document, thus enabling better functional encapsulation within the DOM & CSS.

Shared Array Buffer

Type of ArrayBuffer that can be shared across Workers.

Shared Web Workers

Method of allowing multiple scripts to communicate with a single web worker.

Server Name Indication

An extension to the TLS computer networking protocol by which a client indicates which hostname it is attempting to connect to at the start of the handshaking process.

SPDY protocol

Networking protocol for low-latency transport of content over the web. Superseded by HTTP version 2.

Speech Recognition API

Method to provide speech input in a web browser.

Spellcheck attribute

Attribute for `input`/`textarea` fields to enable/disable the browser's spellchecker.

Scoped attribute

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).

Inline SVG in HTML5

Method of using SVG tags directly in HTML documents. Requires HTML5 parser.

SVG in HTML img element

Method of displaying SVG images in HTML using <img>.

SVG SMIL animation

Method of using animation elements to animate SVG images

Signed HTTP Exchanges (SXG)

Part of the Web Packaging spec, Signed HTTP Exchanges allow a different origin server to provide a resource, and this will be treated as if it came from the original server. This can be used with AMP CDNs, for example, to allow the original URL to be displayed in the URL bar.

text-decoration styling

Method of defining the type, style and color of lines in the text-decoration property. These can be defined as shorthand (e.g. `text-decoration: line-through dashed blue`) or as single properties (e.g. `text-decoration-color: blue`)

URL Scroll-To-Text Fragment

URL fragment that defines a piece of text to be scrolled into view and highlighted.

Screen Wake Lock API

API to prevent devices from dimming, locking or turning off the screen when the application needs to keep running.

Web Serial API

Allows communication with devices via a serial interface.

Web Share API

A way to allow websites to invoke the native sharing capabilities of the host platform

html element: s

svg element: a

svg element: font

svg element: g

svg element: glyph

svg element: hkern

svg element: image

svg element: line

svg element: path

svg element: rect

svg element: set

svg element: stop

svg element: svg

svg element: text

svg element: tref

svg element: view