CSS Container Queries Baseline widely
CSS Layout
Style elements based on the size of a containing element instead of the viewport.
CSS Subgrid Baseline newly
CSS Layout
Nested grid items participate in the parent grid tracks.
CSS Flexbox Baseline widely
CSS Layout
One-dimensional layout for distributing space along a row or column.
CSS Grid Baseline widely
CSS Layout
Two-dimensional layout with explicit rows and columns.
CSS aspect-ratio Baseline widely
CSS Layout
Set a preferred width-to-height ratio on boxes.
CSS gap Baseline widely
CSS Layout
Spacing between flex and grid items without margins.
position: sticky Baseline widely
CSS Layout
Elements stick within a scroll container until a threshold.
CSS Scroll Snap Baseline widely
CSS Layout
Snap scroll positions to defined points in a scroll container.
:has() selector Baseline newly
CSS Selectors
Select an element if it contains descendants matching a selector.
:is() selector Baseline widely
CSS Selectors
Match any selector in a list with shorter specificity rules.
:where() selector Baseline widely
CSS Selectors
Like :is() but always zero specificity.
:focus-visible Baseline widely
CSS Selectors
Show focus rings only for keyboard-style focus.
:not() complex lists Baseline widely
CSS Selectors
Negate multiple selectors in one :not() expression.
OKLCH colors Baseline newly
CSS Colors
Perceptually uniform color space for predictable gradients.
color-mix() Baseline newly
CSS Colors
Mix two colors in a chosen color space in CSS.
CSS custom properties Baseline widely
CSS Colors
Define reusable --token values with cascade inheritance.
currentColor keyword Baseline widely
CSS Colors
Use the computed text color as a fill or border value.
clamp() sizing Baseline widely
CSS Typography
Fluid values bounded by minimum and maximum sizes.
Variable fonts Baseline widely
CSS Typography
Single font files with adjustable axes like weight and width.
line-clamp Baseline widely
CSS Typography
Truncate multi-line text after a set number of lines.
text-wrap: balance Baseline newly
CSS Typography
Balance headline line lengths for nicer rag.
Fetch API Baseline widely
JavaScript
Promise-based HTTP requests replacing XMLHttpRequest.
async/await Baseline widely
JavaScript
Syntactic sugar for promise-based asynchronous code.
Optional chaining (?.) Baseline widely
JavaScript
Safely access nested properties when intermediates may be null.
Nullish coalescing (??) Baseline widely
JavaScript
Default values only when left side is null or undefined.
Top-level await Baseline newly
JavaScript
Await promises at module top level in ES modules.
Private class fields (#) Baseline widely
JavaScript
True private fields on class instances.
structuredClone() Baseline widely
JavaScript
Deep-copy structured data including typed arrays and Dates.
Array.prototype.at() Baseline widely
JavaScript
Relative indexing including negative indices.
Object.hasOwn() Baseline widely
JavaScript
Safer own-property check than hasOwnProperty.call().
RegExp lookbehind Baseline widely
JavaScript
Match patterns preceded by a fixed-width lookbehind assertion.
Intersection Observer Baseline widely
DOM APIs
Observe element visibility relative to a root for lazy loading.
Resize Observer Baseline widely
DOM APIs
React to element content-box size changes.
Mutation Observer Baseline widely
DOM APIs
Watch DOM tree and attribute mutations asynchronously.
Custom Elements Baseline widely
DOM APIs
Define reusable autonomous HTML tags with JavaScript classes.
Shadow DOM Baseline widely
DOM APIs
Encapsulated DOM and styles for web components.
<dialog> element Baseline newly
DOM APIs
Native modal and non-modal dialog with ::backdrop.
Popover API Baseline newly
DOM APIs
Top-layer popovers with popover attribute and showPopover().
Declarative Shadow DOM Baseline newly
DOM APIs
Server-render shadow roots with a <template shadowroot>.
localStorage Baseline widely
Storage
Key-value string storage persisted per origin.
IndexedDB Baseline widely
Storage
Structured transactional database in the browser.
Cache API Baseline widely
Storage
Request/response cache used by service workers.
sessionStorage Baseline widely
Storage
Key-value storage cleared when the tab closes.
WebSockets Baseline widely
Network
Full-duplex communication channel over a single TCP connection.
Service Workers Baseline widely
Network
Programmable network proxy for offline and push workflows.
Web Push Limited availability
Network
Push notifications from a server via service workers.
Beacon API Baseline widely
Network
Send analytics on page unload without blocking navigation.
Streams API Baseline widely
Network
Readable and writable byte streams for incremental I/O.
WebGL 2 Baseline widely
Graphics
GPU-accelerated 2D/3D graphics with GLSL ES 3.00.
WebGPU Baseline newly
Graphics
Modern GPU compute and rendering API succeeding WebGL.
Canvas 2D Baseline widely
Graphics
Immediate-mode 2D drawing to a bitmap surface.
OffscreenCanvas Baseline widely
Graphics
Render to canvas in a worker without DOM coupling.
SVG filters Baseline widely
Graphics
Apply blur, color matrix, and other filter primitives in SVG.
WebRTC Baseline widely
Media
Peer-to-peer audio, video, and data channels.
Media Source Extensions Baseline widely
Media
Append media segments for adaptive streaming players.
Picture-in-Picture Baseline widely
Media
Floating always-on-top video window.
WebCodecs Baseline newly
Media
Low-level audio/video encode and decode in JavaScript.
Web Cryptography API Baseline widely
Security
Subtle crypto for digest, sign, encrypt in secure contexts.
Credential Management Limited availability
Security
Programmatic access to stored passwords and federated credentials.
Trusted Types Limited availability
Security
Enforce typed sinks to mitigate DOM XSS.
