In bug #1397645, I was asked to open a new bug related to my problems while trying to upload videos on youtube. I previously opened a bug, which was closed as duplicate of #1397645, bug #1398556. All details are in duplicate bug report. I thought fix for bug #1397645 will give me back upload on youtube, but not. I'm still blocked, even using 12 september 2017 nightly, based on commit https://hg.mozilla.org/mozilla-central/rev/b0e945eed81db8bf076daf64e381c514f70144f0

[Tracking Requested - why for this release]: Assuming this is a regression, we can't ship with uploading broken on youtube. Frederic, does this happen only on Nightly? Not beta or release?

Sorry for this late answer. All tests done here with addons disabled. Tested with two files : * a m4v file known as ISO Media, MP4 v2 [ISO 14496-14] - 217.3 Mb * a mp4 file known as ISO Media, MP4 Base Media v1 [IS0 14496-12:2003] - 29.7 Mb I) Nightly reports : Using nightly based on this commit : https://hg.mozilla.org/mozilla-central/rev/a73cc4e08bf5a005722c95b43f84ab0c8ff2bc7c Both uploads are broken. Size doesn't seems to matter here. II) Firefox 56.0 beta : With latest beta which seems to be 56.0b11. For both files, upload is started in less than a second after import progress page is displayed... So there is a bug in nightly code.

@Reproter, Just confirmation, The regression window is stated in bug 398556 comment#0, is it correct?

I submitted a patch on bug 1398556.

(In reply to Alice0775 White from comment #3) > @Reproter, > Just confirmation, The regression window is stated in bug 398556 comment#0, > is it correct? Yes it is. Sorry for lateness in the answer.

The duplicate is fixed in 57, not tracking.