Hi dementius, I'm also on macOS and using Firefox 72.0.2 , but Youtube videos play fine here.

Let' figure out what different about your setup, that is causing the problem. First, let's try something simple, like clearing your cache and cookies.

1. Click the Library button and choose History.
2. In the History menu, choose Clear Recent History.
3. In the Time Range to clear drop-down, select Everything.
4. Click the arrow next to Details to display the list of items that can be cleared.
5. Select both Cookies and Cache.
6. Click Clear Now.

If the problem still occurs, let us know.

Hi Chris, thanks for standing by. Before I clear all my cookies and cache, let's consider the messages I recieve from invidio. Reads 'media playback was aborted due to a corruption problem or because the media used features your browser did not support. ' I slightly hesitate to clear all cookies and cache, I don't know what I'll lose, but I'll do it if I must. To me, and I'm very much an old pooper here, (hence the handle), the message sounds as if my privacy settings are blocking the play. In Youtube, the little 'thumbnails' play, but I get the little spinning ball, intermittently, and then a similar but less specific message from YT and no play. Is there anything we can try before deletion ? My preferences in the privacy panel are set to 'standard', and as I said, it was working before on this iteration of firefox. Most perplexing...

Is there some way of 'return to factory settings ' ? I'm pretty sure I've done something to break this...

Hi dementius,

I can certainly offer you other options AND set your mind at ease about clearing cache and cookies. ☺️

As a troubleshooting step, you can test the issue in Firefox Safe Mode. Safe Mode is a troubleshooting tool that will disable your add-ons as well as some other things which will help you narrow down the cause of the problem To start in Safe Mode, go to Help > Restart with Add-ons Disabled. If the problem does not occur in Safe Mode, then you can disable your extensions one-by-one until you find out which one is causing the problem. For more info, visit Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems.

Regarding what you will lose by clearing cache and cookies...

Cache temporarily stores images, scripts, and other parts of websites you visit in order to speed up your browsing experience. By clearing it, you are forcing the data to be redownloaded from the site. You should hardly see any affect at all on your web experience.

Cookies are stored on your computer by websites you visit and contain information such as site preferences or login status. The only impact of any importance is that you will have to log back into sites that just remembered who you are.

In both cases, the data is only meant to be stored temporarily anyway, and it actually good for privacy and security to clear them.

In addition to those options, if you are at all worried about losing data, you can always create a backup of your Firefox data. Since you're on macOS, it should already be included in your Time Machine backup. If not, there are instructions in the following article: Back up and restore information in Firefox profiles

To return to factory settings... There is a Refresh feature in Firefox that should include what you want. This will purge a lot of your Firefox files, while retaining most of your personal data. For instructions, check out the following article: Refresh Firefox - reset add-ons and settings

Hopefully you now feel better about troubleshooting the issue. ☺️ If you need more hands-on help, I can start up Skype, and we do a screensharing session, and I can walk you through it if you'd like. Tell us how it goes.

Hey Chris, that is a fantastically great information ! Thanks ! I guess I'll try the deletion route first, since you set my mind at rest about data loss.

The only extension I'm running is privacy badger. Unless ypu count the duckduckgo thing.

The 'refresh' suonds way scary, what with all the purging and such terrifying propositions. 'Most' is also rather unnerving....

I shall try the cookie-delete now.

Hey Chris, that fixed it ! It also dumped me outb of this conversation, foxed me for a while...

Thank you, thank you !

May I impose on your patience just a little longer to ask you to try to explain, in terms I might understand, HOW a cookie, or something that found its way into my cache, could have caused this kind of a problem ?

.....Andrew.

Oh dear, the problem has immediately returned.

I managed to test-play one video, and now the same thing happens..

Something is going on here...

Any more ideas ?

Problem persists after restart in safe mode.....

Oddly, a very few vids DO play, very few.....

Something very strange.

...Andrew.

Can you repeat the cookie and cache clearing again, and see if this helps (temporarily) a second time? This may be diagnostic.

I tested the DDG privacy essentials extension and have no video problems with it.

-- HOW a cookie, or something that found its way into my cache, could have caused this kind of a problem ?

Cookies generally contain various settings (you have seen what deleting an active login session cookie does when deleted - it kicked you out of your help thread). Some of these settings with respect to video hosting sites will contain information on what format and quality of file or stream to send you, including preferences you have set, such as the video quality from the list available (auto, 480p, 720p, etc.). It will also contain more technical settings. If the cookie is corrupted, or the site incorrectly detects a capability of your hardware, operating system, or software, that cookie can break things until it expires or is deleted.

The cache is the home of temporary web page files. There might be something broken in there as well, causing pages from the cached site to not work correctly.

--

If clearing cookies and cache again leads only to a temporary, or no fix, you might try the other two suggestions Chris Ilias posted: Staring Firefox in Safe Mode, and Refreshing Firefox. Note that refreshing FF is semi-destructive (but you get a back-up), so please read the linked article.

You might also simply try a new, clean user profile to test, before Refreshing Firefox.

Type about:profiles in the address bar, and Enter. Click Create a New Profile Give it a name. Do not "choose folder" Click Finish Scroll to the new profile Click Launch Profile in new Browser Close the original browser window Test your problematic video sites.

Hi CG,

Tried safe mode, no joy. So I see that I can clear the cookies, site data and cache from the 'browser privacy' panel. Is that equivalent of what Chris said ?

I also note that Peertube and Opentube sites are not affected with this problem....

I also note that some videos play, just not the ones I want to watch ! I also note that sometimes when addressing a video, the writen subtitle is the one addressed but the static picture is another previously addressed one. I tried deleting cookies and site data again a couple times, and no joy. In hindsight, I think the previous supposed temporary fix was not a fix, it was just that I tried one of the videos that do play as the first trial. How coincidentally cruel is that ? So, I'm now trying to play the grateful dead 'ripple', and instead of getting the error message, i'm just getting the eternal loading pinwheel. Something is very wrong here. There may be more than one problem. There may be a problem with the browser remembering where it was last, and there may be a problem with yt, maybe they hate me. I've heard that goo are starting to f, mess with thoseb people from whom they are not profiting. Could this at least partially be corporate strangulation ?

I'm in the uk, could that be relevant ?

....A2.

Firefox has deffinately 'lost it's place' when accessing yt videos. Mostly, it displays the video previously accessed. This was something I had noticed before the 'crisis' point yesterday. Occasionally. Something is very broken.

Hi Andrew, If clearing cookies and cache didn't work, and Safe Mode didn't work, I think it's time to refresh Firefox. Could you please try the instructions in the following article: Refresh Firefox - reset add-ons and settings

You appear to have some content blocking extensions installed

If you use extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) that can block content (Adblock Plus, NoScript, Disconnect PE, DuckDuckGo, Ghostery, Privacy Badger, uBlock Origin) always make sure such extensions do not block content.

• make sure your extensions and filters are updated to the latest version
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

Firefox shows an highlighted shield icon at the left end of the location/address bar in case Tracking Protection is blocking content.

• click the shield icon for more details and possibly disable the protection

You can check in the Web Console what content is blocked.

• "3-bar" menu button or Tools -> Web Developer
• https://support.mozilla.org/en-US/kb/enhanced-tracking-protection-firefox-desktop

Hi CG, Chris and cor-el, thanks for all the suggestions.

CG, Could you explain a bit about the 'profile '?

Chris, what about CGs profile suggestion ?

Cor-El, I've tried restarting in safe mode, also tried manuallu disabling the badger and the ETP in Firefox, all to no effect.

I am having considerable difficulty with this, YT is playing videos from users I have never accessed, and none from my usual ones. It is also displaying the picture from the previous attempted video in the pane of the present requested one, just before it gives the blank screen and error message. I have just tried restarting the laptop, and upon restarting firefox, the previous 'session' was not restored. How do I restore it ?

I'm sorry to be so inept here, thank you all for your patience and continued help.....

Okay, so now after having restarted the laptop, and having had to re-launch firefox from the finder (I can't seem to get it to persist in the dock), and having lost the previous session of 3 windows with multiple tabs, YT appears to be working again, for now. There is still an intermittent problem of displaying the previously selected video in stead of the current one. I get the impression that this will get worse again.

Hi Andrew, I'm not sure I understand what you mean by "displaying the previously selected video in stead of the current one".

Would you mind sending us a screenshot of what you're seeing? For instructions, see How do I create a screenshot of my problem?.

Hi Chris, and thanks again for taking an interest; appreciated....

Well, of course, it's like taking your car to the mechanic: see this ? It won't do it now... Still I'll try to be more specific.

For example, I enter a search criterion into the youtube search box, let's say 'brexit' in this case. So youtube displays a list of videos. I select a video to play, maybe it plays, maybe it doesn't (seems to be working just now). Either way, I back-up to the list again and select another video. Now, the title of the selected video appears underneath the video frame, but a picture from the previous video appears IN the frame, stalled. I'll grab it for you next time it happens, but it is not going to be any more instructive than the description above. After all, what's to see ?

The laptop restart was quite 'destructive', and I had to find firefox in the finder. reloading it lost all my saved stuff on various sites, and the 'restore session' had been un-checked so I lost it all, I guess.

Could you tell me some way of getting the firefox icon/disc image to persist on the desktop or in the dock through restarts ? It is always a pain and deters me from software updates....

Thanks for all your help ! ......A2.

OK, is your Firefox even properly installed? One thing to note is that when installing, you should manually open the DMG and drag the Firefox.APP to the Applications folder. (For some reason, automatic installation from the DMG causes issues.)

You may wish to uninstall the current installation, then download a new copy (or use the DMG you previously downloaded if you still have it, if it is up to date).

Run Firefox. When the icon appears in the dock, right-click or control+click the icon, and select Keep in Dock.

______

The laptop restart was quite 'destructive', and I had to find firefox in the finder. reloading it lost all my saved stuff on various sites, and the 'restore session' had been un-checked so I lost it all, I guess.

I am not sure what is happening in the laptop restart, but it sounds like Firefox defaulted to a different profile (the place all your personal settings and data are kept). If you type into the address bar about:profiles and Enter, you can see a list of all profiles associated with your Mac login.