Shared MessagePort for AudioWorklet

Category: Multimedia
Type: Chromium catches up
Status: Proposed (Chrome Proposed)
Intent stage: None

Breaking change: No
Enterprise impact: None
Chromium flag: enable-experimental-web-platform-features
Spec maturity: Published standard
Web Platform Tests: Yes

WPT details: https://wpt.fyi/results/webaudio/the-audio-api/the-audioworklet-interface/audioworklet-messageport.https.html

Summary

Exposes a shared MessagePort on AudioWorklet and AudioWorkletGlobalScope. This lets web applications communicate directly between the main thread AudioWorklet and the AudioWorkletGlobalScope without creating a bootstrap AudioWorkletProcessor only for message passing.

Motivation

The Web Audio specification defines a shared MessagePort on AudioWorklet and AudioWorkletGlobalScope. This lets web applications communicate directly between the main thread and the AudioWorkletGlobalScope without creating a bootstrap AudioWorkletProcessor or AudioWorkletNode only for message passing. Without this capability, developers have to keep workaround code that instantiates dummy processors solely to transfer initialization data or control messages into the worklet global scope. This adds code complexity and runtime overhead, and prevents cleanup of compatibility hacks in upstream projects. This change aligns Chromium with the current Web Audio specification and existing interoperable behavior. It also restores compatibility for real-world code that expects audioContext.audioWorklet.port to exist, including Emscripten-generated applications and demos such as the MOD player discussed in the linked issue. Relevant specification and ecosystem discussion: - https://github.com/WebAudio/web-audio-api/issues/2456 - https://github.com/WebAudio/web-audio-api/pull/2507 - https://github.com/emscripten-core/emscripten/pull/25354

Standards & signals

Specification: https://webaudio.github.io/web-audio-api/#dom-audioworklet-port
Firefox: Shipped/Shipping — Shipped in Firefox 138
Safari: No signal
Web developers: Positive
Tracking bug: https://issues.chromium.org/issues/446920095

Ecosystem

Web Platform Tests: https://wpt.fyi/results/?q=webaudio%2Fthe-audio-api%2Fthe-audioworklet-interface%2Faudioworklet-messageport
Chrome Platform Showcase: https://chrome-platform-showcase.paulkinlan-ea.deno.net/features
GenDN reference: https://gendn.paulkinlan-ea.deno.net/features
chrome.dev demos search: https://www.google.com/search?q=site%3Achrome.dev+Shared%20MessagePort%20for%20AudioWorklet
MDN Web Docs: https://developer.mozilla.org/en-US/search?q=Shared%20MessagePort%20for%20AudioWorklet
Baseline status: https://webstatus.dev/?q=Shared%20MessagePort%20for%20AudioWorklet

Docs: https://developer.mozilla.org/docs/Web/API/AudioWorkletGlobalScope/port

Explainers: https://github.com/WebAudio/web-audio-api/issues/2456 https://github.com/WebAudio/web-audio-api/pull/2507

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