Browser support

Which browsers a WebFluent site targets, and what each newer platform feature falls back to where it is missing.

A WebFluent site targets the current versions of Chrome, Edge, Firefox and Safari, on desktop and mobile — the browsers that update themselves. The output is plain HTML, CSS and modern JavaScript (ES2020); there is no polyfill and no legacy build.

A static build's pages are readable with no JavaScript at all; everything interactive needs it.

Features with a fallback

Features with a fallback
Feature Used for Where it is missing
View Transitions API

Router(transition: …), shared: elements

The class-based transition plays instead; shared: does nothing

linear() easing

easing: .spring, .bouncy

 The browser ignores it and uses its default easing
Web Animations API

enter, exit, list moves, count:

 Everywhere current; without it, elements appear and leave without motion

IntersectionObserver

on: .enterView

 The animation plays at once
Background Sync writes kept offline, sent after the tab closes The page sends them the next time it is open and online
Service workers

offline

 The site works online as usual
WebRTC

peer

The peer reads error: "WebRTC is not available in this browser"

BroadcastChannel

channel

The channel reads closed
Network Information API

network.effectiveType, .saveData, .downlink

null; network.online works everywhere

Intl

format, ago, plural forms

 The build's own table for the common locales
Container queries

@container in a style block

 Passed through as written; the rule does not apply

:focus-visible

 focus rings Focus rings on every focus

Dialogs and forms

Modal and Dialog use the <dialog> element and showModal(), which every current browser has. Validation uses the browser's constraint validation alongside the language's rules.