User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:69.0) Gecko/20100101 Firefox/69.0

Steps to reproduce:

• open a link on twitter containing youtube video. (e.g. https://twitter.com/mozilla/status/1182459301543186439)
• play video
• click on fullscreen button

Actual results:

the video doesn't change to full screen.

Expected results:

the video should change to full screen.

Hi Clément!
According to this youtube help, this is expected behavior. https://support.google.com/youtube/answer/72689?visit_id=637069213418403489-4003127998&rd=1

If you agree, I'll close this issue whit Works For Me.

I think this is not expected behavior: video can be toggled full-screen on others browsers.

I guess that should fix it: https://bugzilla.mozilla.org/show_bug.cgi?id=711276

I'll add Product and Component so the corresponding team can take a look at this.

The priority flag is not set for this bug.
:drno, could you have a look please?

For more information, please visit auto_nag documentation.

(In reply to Clément from comment #2)

I think this is not expected behavior: video can be toggled full-screen on others browsers.

I can't find a browser on OSX that allows this, which platform was that?

which browser versions did you use on OSX?

According to MDN, chrome 60, opera 47 and safari 11.1 support allow HTML attribute https://developer.mozilla.org/en-US/docs/Web/HTML/Element/iframe#Browser_compatibility

I just test it on Ubuntu with Firefox 71 and Chromium 79

• Chrome support both allowfullscreen and allow="fullscreen"
• Firefox only support allowfullscreen

My test: https://codepen.io/yukulele/pen/YzPeVZE?editors=1000

Hi, I managed to reproduce this issue using this URL: https://codepen.io/yukulele/pen/YzPeVZE?editors=1000.

• allow="fullscreen" does not work on Firefox

Affected version:
latest Nightly Version 74.0a1 Build ID 20200106215403
Beta Version 73.0b2 Build ID 20200107212705
Release Version 72.0 Build ID 20200103162918

Affected Platform:
Windows 10, Ubuntu 18.04 and macOS 10.15

(In reply to Clément from comment #7)

which browser versions did you use on OSX?

Latest Chrome Stable and Canary, Firefox Nightly, Safari stable. In all cases, I see something like the attached screenshot.

(In reply to Clément from comment #2)

I think this is not expected behavior: video can be toggled full-screen on others browsers.

I'm sorry, I thought this was a web-compat issue with twitter, and I was confused because no browser allow full-screen for me. Do you have a browser on OSX where you can use youtube's own interface to trigger full-screen?

I'm just wondering if we should just dupe this against bug 711276, or if there is something else here? Maybe I'm doing something wrong? I'm not logged in on Safari or Chrome, for example. I don't have extensions on those browsers either.

In any case, I can certainly see the issue with your latest test case, but this is clearly bug 711276.

On chrome I can't fullscreen if i'm logged out but I can if i'm logged in
On firefox I can't even if i'm logged in

Ok, I can repro now. Not sure why it's different when logged in but this is now a web compat bug: either we need to implement allow="fullscreen", or we need to have twitter use the other variant.

As you note in comment 2, this is now blocked on bug 711276, I've asked a DOM person to have a look.

Thanks you very much for taking the time to follow up!

As noted in bug 711276 comment 14 Twitter appears to give us markup that's different from Chrome. I've emailed them about that. I filed bug 1608358 on the test from Clément. Thanks for writing that!

According to comment7, this issue is caused by lacking of a support for allow="fullscreen" on iframe. Change to DOM component to put this issue on their radar.

The STR from the bug report does not reproduce the bug, but I guess that it's due to the addition of the allowfullscreen attribute to the <iframe> element.

According to comment 15, this bug is about the lack of support for allow="fullscreen" on iframes. Bug 1608358 has a patch for this, so I'm going to mark this as a duplicate of that.