Hi hugocoisas, In the version 70 Release Notes: "Social tracking protection, which blocks cross-site tracking cookies from sites like Facebook, Twitter, and LinkedIn, is now a standard feature of Enhanced Tracking Protection. "

You can use Custom Privacy & Protection settings instead.

I added youtube to all exceptions but the problem remains.

hugocoisas, I have to apologize - I REALLY misunderstood your question.

Try turning off Enhanced Tracking Protection: select the Shield icon at the left end of the address bar and move the slider to the left. Refresh the page.

If that doesn't help: Try disabling your extensions. You may need to restart Firefox.

I'm having this issue too. Disabling enhanced tracking protections has not solved the problem.

You can try Clearing Cookies and Site Data for that site by clicking on the padlock at the left end of the address bar and selecting Clear Cookies and Site Data... Note that this will log you out. Then Refresh the page.

I've already tried that as well, and I cleared my entire cache and data for firefox. Didn't do anything

You can try Firefox in it's Safe Mode. Safe Mode temporarily turns off hardware acceleration, resets some settings, and disables add-ons (extensions and themes) that might be causing problems. See: Troubleshoot Firefox issues using Safe Mode https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode

Starting in safe mode did not fix the problem either.

You can try the suggestion in this thread:

Youtube is acting weird https://support.mozilla.org/en-US/questions/1173622

Otherwise, you might have to consider Refreshing Firefox:

Refresh Firefox - reset add-ons and settings https://support.mozilla.org/en-US/kb/refresh-firefox-reset-add-ons-and-settings

Unfortunately none of these have really worked yet. It's so weird because a couple of days ago it worked fine and it still works on the other browsers.

I didn't change anything in regards to firefox and I only installed the update when I was already trying to fix this issue.

Well, hold off on the Refresh suggestion. Some people end up having serious problems with it.

Besides, it might be something easier. If someone else knows..

If you're familiar with Profiles, you can create a new Profile to test with. That might give a better idea where the problem is.

Uninstalling Firefox, deleting all my local data for it from my computer, and then restarting and reloading everything fixed the problem. I'd still like to find out what caused this.

So would I but, it's too late now. What else is weird is that I have Strict Content Blocking and other extensions at work - I'm even blocking youtube.com - and Youtube works fine for me. Go figure, huh.

Anyway, I'm glad that you got it working. Don't stay up too late binge-watching.

Browse Safe!

Yes! Uninstalling did the trick. Thank you all for the sugestions and for helping me solve this annoying problem.

I've also been having this problem too. It only occurred very recently.

I've tried all sorts: Plugins, safe mode, Pi-hole config / disabling, DNS flushing, checking the inspector for hints....and then I realised that YouTube was serving webp for these thumbnails and I'd changed a setting that might be causing this.

In short, I didn't like that saving an imagine from Firefox was a webp a while back. I couldn't send them on WhatsApp via a browser as the format was unsupported.

I'd changed 2 settings in about:config

image.webp.enabled was set to false (default true) image.http.accept was set to "*/*" where the default was "image/webp,*/*" - all without the quotes

As soon as I changed these back, they instantly started working. I suspect a reinstall resets these, hence why that fixes it. I didn't realise that safe mode didn't change these values back to default.

Hopefully this may help others.

Agent said

I'd changed 2 settings in about:config image.webp.enabled was set to false (default true) image.http.accept was set to "*/*" where the default was "image/webp,*/*" - all without the quotes As soon as I changed these back, they instantly started working. I suspect a reinstall resets these, hence why that fixes it. I didn't realise that safe mode didn't change these values back to default. Hopefully this may help others.

Thanks for this! Just changed these two settings in about:config and it immediately fixed the issue for me. Highly suggest others try this out before going for a full re-install.

This exact same problem also occurs to me. But just when I am logged in in YouTube. When I'm signed off I can see all thumbnails as normally.

The helpful answer from Agent above solved it! :)

Agent said

I've also been having this problem too. It only occurred very recently. I've tried all sorts: Plugins, safe mode, Pi-hole config / disabling, DNS flushing, checking the inspector for hints....and then I realised that YouTube was serving webp for these thumbnails and I'd changed a setting that might be causing this. In short, I didn't like that saving an imagine from Firefox was a webp a while back. I couldn't send them on WhatsApp via a browser as the format was unsupported. I'd changed 2 settings in about:config image.webp.enabled was set to false (default true) image.http.accept was set to "*/*" where the default was "image/webp,*/*" - all without the quotes As soon as I changed these back, they instantly started working. I suspect a reinstall resets these, hence why that fixes it. I didn't realise that safe mode didn't change these values back to default. Hopefully this may help others.

I've changed only image.webp.enabled back to true and it did it for me.

Unfortunately it's inconvenient as I'd like to drag'n'drop images as jpg, some programs don't accept webp, and changing extension doesn't always work..