Cobalt Support Quick Reference

HTML elements

<a>
<audio>
<body>
<br>
<div>
<head>
<html>
<link> (with type="text/css")
<lottie-player>
<meta>
<script>
<span>
<style>
<title>
<video>

CSS properties

CSS selectors

Simple selectors: '*', type, .class, #id, :empty, :focus, :not()
Pseudo elements: :before, :after,
Combinators: ' ', '>', '+', '~'
Grouping with ','

JavaScript Web APIs

Crypto.getRandomValues
CSSOM (partial)
CSSOM View (no scrolling, moving, resizing)
Console.log
CORS
DOM4 (partial)
EncryptedMedia Extensions v0.1b (unprefixed)
Fetch (supports text(), JSON(), arrayBuffer(), types)
Image (for preloading and caching only)
Intersection Observer
Media Session
Media Source Extensions, Editor's Draft 09 August 2012
Streams API
SubtleCrypto
Typed Arrays (partial)
URL (partial)
Web Audio API (partial)
Web Storage API
WebIDL Level 2
WebSocket API
window.atob() and window.btoa()
XMLHttpRequest Level 1

Protocols

https:
h5vcc-embedded: (for embedded resources)
Content Security Policy Level 2 in HTTP headers is required, and report-only is disabled.
QUIC
SPDY

Media formats

Containers

FLV
MKV (for WebM)
MP4/FMP4
WAV

Encodings (depending on platform support)

16-bit stereo PCM audio (for sound effects)
AAC
AV1
AVC (H.264) at 1080p/60fps (Level 4.2)
Dolby Digital (AC-3)
Dolby Digital Plus (Enhanced AC-3, or EAC-3)
HEVC (H.265)
VP8/Vorbis
VP9/Opus

Images

JPEG
PNG
WebP (including animated)

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Last updated 2025-09-03 UTC.