Spec Clarification: Autoplay Behavior on Extension Pages

[hanguokai]

Autoplay on Web

On the web, browsers typically restrict the autoplay behavior of web pages. For more details, see the following links:

• MDN: HTMLMediaElement: play() method
• MDN: Autoplay guide for media and Web Audio APIs
• Chrome: Autoplay policy in Chrome
• Chrome: HTMLMediaElement.play() returns a promise
• Stackoverflow: How to handle "Uncaught (in promise) DOMException: play() failed"

Autoplay on Extension Pages

However, there is no documentation or specification indicating whether this behavior is equally effective on extension pages.

The goal of this issue is to clearly define its behavior in the (Web or Browser Extensions) specification and implementation.

Some Situations:

• autoplay in extension top frame
• autoplay in extension page's subframe that may be a web page, extension page or extension sandbox page.
• autoplay in web page's subframe that is an extension page or extension sandbox page.
• content script (Isolated world): control HTMLMediaElement.play()

Some Use Cases:

• The AUDIO_PLAYBACK reason in the offscreen document.
• Foreground or Background radio playback.
• Scheduled audio playback (alarm clock).

Currently, browsers seem to exempt extensions from this restriction in most cases. If so browsers need to clarify this behavior. But if we have concerns about this behavior, perhaps we can consider adding a new autoplay permission in the future (that will cause breaking change), like the notifications permission, or some other ways. Whether it should be looser or stricter, it's an undefined place at the moment. Of course, from a developer's perspective, since there is no sensitive data involved, and there are web store policy requirements, it would be better to be lenient.

PS: I open this issue because there is a discussion about it today.

[robbi73]

About the specific pattern: autoplay in extension page's subframe that may be a extension sandbox page I can confirm that nowaday all chromium based browser (but Chrome itself) don't throw any error attempting to invoke play() in extension sandbox page. No interation is required as well. I made some tries with:

• Edge v. 125.0.2535.67
• Iron v. 123.0.6250.0.
• SlimJet v. 122.0.6261.39
• Naver Whale v. 124
• Brave v. 125.0.6422.112

Chrome, on the other hand, when we invoke play() in the sandbox iframe throws: play() failed because the user didn't interact with the document first. Only after clicking on the sandboxed iframe the playback can be attempted again.