MediaSource sourceopen event does not fire when video preload attribute is set to "none"

Assigned to



3 years ago
4 months ago


(Reporter: iamcraigcampbell, Assigned: jya)


41 Branch

Firefox Tracking Flags

(platform-rel -)


(Whiteboard: [platform-rel-Vimeo])



3 years ago
User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36

Steps to reproduce:

Example URL:

1. Go to example page
2. Click each button

Actual results:

"Source open fired" is fired for every preload type except for "None".

Expected results:

The sourceopen event should fire and "Source open fired" should be printed under the "Results" section on the page for all preload types.


I couldn't find anything in the MediaSource or Video/MediaElement spec defining what the behavior should be here, but I don't think the preload attribute should affect MediaSource playback in any way. 

For reference this works as expected in Safari 8, Safari 9, IE 11, and Edge. It does NOT work in Chrome, and I made a ticket there too

If it is expected behavior it should at least be well documented or there should be a warning that the MediaSource API does not work when the preload attribute on the video is set to "none".

Comment 1

3 years ago
For reference a bug was filed against the spec by a member of the Chromium team.
Priority: -- → P2


3 years ago
Assignee: nobody → jyavenard
Component: Audio/Video → Audio/Video: Playback

Comment 2

3 years ago
The MediaSource spec was updated yesterday to confirm that the preload attribute should be ignored:
Mass change P2 -> P3
Priority: P2 → P3
platform-rel: --- → ?
Whiteboard: [platform-rel-Vimeo]
platform-rel: ? → -
Ever confirmed: true
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