I set media.block-autoplay-until-in-foreground to false and hard-reloaded.

I did not work initially but now it seems to be working. Although I'm not sure whether these actions fixed my issue whether it's just the inconsistency of the behavior that led to the temporary expected behavior.

I'll update this thread later.

Try staying signed out of your Youtube account.

Does it still happen if the playlist is in a dedicated window that is always visible?

I did notice that there were difference in terms of behavior whether I had an interaction with the player directly from the browser window (like clicking on the play button), or pressing play from my headphones without going back to the browser. And the playlists seem to be working when I'm actually watching videos (however I need confirm it for I move left and right and I may interact with the browser without noticing it -. However staying logged off does not seem to have any impact, since it failed to work in incognito mode - where I'm logged off -.

Since I cleared the cache it seems to be working as it should, but it may be too early to celebrate for I've had a few smooth afternoons of working playlist until they suddenly don't.

I'll keep you updated if it starts behaving unexpectedly again, and I'll try running the playlist with a visible and focused browser.

Hello again,

So it stopped working again today.

I did try to hard-reload, but it would not help.

The playlist do seem to work as expected when in the foreground and seem to be failing to play automatically in the background (despite `media.block-autoplay-until-in-foreground`being set to false. Videos open in a new tab through the mouse's scroll button do launch in the background though. It just does not apply to playlists).

While this issue is minor it is quite the pain in the butt.

Opening youtube playlists in a new background tab consistently autoplay for me with media.autoplay.default set to 0 ("Allow Audio and Video") and media.block-autoplay-until-in-foreground set to false. Middle-clicking on "VIEW FULL PLAYLIST" will not autoplay.

Are you sure ad blocking is not interfering? Does it still happen in Troubleshoot Mode?

Right now the playlist seems to be working in troubleshoot mode, which would indeed indicate an issue with uBlock origin if this does not end up being a mere fluke.

Which I find surprising, considering that I haven't seen many complaints about ublock and playlists.

Maybe the issue comes from YouTube in an attempt to make Adblock users' experience sub-optimal ?

I'll keep running tests and I'll keep you updated if anything new comes up.

Thanks for your help so far !