Firefox 127.0.2 fixes Google-caused YouTube playback issue

Martin Brinkmann
Jun 25, 2024

Mozilla released a new version of its Firefox web browser a moment ago. Firefox 127.0.2 fixes a long-standing playback issue on YouTube that was caused by the Google-owned property and not Firefox according to Mozilla's analysis of the issue.

For the past five or so months, some Firefox users were running into roadblocks regularly on YouTube. The full number of affected users is unclear. We published an article about the issue just last week.

Here are the details:

  • It affected regular and live videos on YouTube, but not all of them.
  • vp9 videos with a resolution of 1080 or higher were affected only.
  • Affected users noticed an endless buffering issue.

Mozilla kept track of two main bugs. These were bug 1900191, which dealt with the live video problem, and bug 1878510, which dealt with the problem when watching regular videos on YouTube.

Firefox 127.0.2

It took Mozilla some time to analyze the issue and come up with a solution. Core reasons for that were that the engineers could not replicate it at first, even when accessing the same videos on YouTube.

After a while, Mozilla engineer Alastor Wu discovered the root cause of the issue. He said that the issue has been caused by bad muxed VP9 bytestreams served by YouTube. The issue was caused by Google-owned YouTube therefore according to Mozilla and not a bug in the Firefox web browser itself.

Here is a quick summary of Wu's technical analysis of the issue: YouTube served bad video samples that overlapped with previously served ones. This should not happen, and is the cause of the problem. The overlapping caused Firefox to fail the calculation of the next sample, which would in the end trigger the endless buffering state. You can check the full comment by following this link.

The release notes state: "Fixed an issue where YouTube playback may experience stalling under certain conditions."

Closing Words

Mozilla did not mention why Chromium-based browsers were not affected by this. One possible explanation is that it is using a different kind of error-handling when running into the issue. Ultimately, it was Firefox and Firefox-based browsers that were affected by the issue only.

Affected Firefox users may upgrade the browser to the latest version immediately. This should fix the issue.

The easiest option to do so on the desktop is to select Firefox Menu > Help > About Firefox. This displays the current version and downloads the latest update that is available.

Mozilla released Firefox 127 earlier this month. It introduced a small number of changes, including security updates.

Do you use Firefox and play videos on YouTube using the browser? What has been your experience in the recent past?

Firefox 127.0.2 fixes Google-caused YouTube playback issue
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Firefox 127.0.2 fixes Google-caused YouTube playback issue
Firefox 127.0.2 fixes a long-standing issue on YouTube that caused endless buffering during playback of some videos.
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  1. Gh said on June 30, 2024 at 8:53 pm

    All I have to say is that firefox codec support has issues. A solution is to just do it with ffmeg and stop trying with vmf. I am very dissapointed with firefox’s hevc implenation too. It sti? has issues and fails to direct play hevc in all media servers plex, emby and jelly. Chromium hevc implenation is perfect.

  2. vgtz said on June 29, 2024 at 2:59 pm

    Had experienced some glitches with Ytube before but not recently…
    Anyway, as I decided to install NoScript in Chrome and Edge (not recomended by Google…) and started visiting some sites, had a very pleasent surprise… Using Chrome and Edge, when you visit some sites and then that only installs 1 script (it’s own) you are tracked around by these sites with scripts!
    Firefox does not allow this tracking around… This is huge because scripts are getting more complex day by day.

  3. Timothy said on June 27, 2024 at 11:13 am

    Complete misdiagnosis of whatever is going wrong. I never use above 720p and have been experiencing these buffering issues since the YT overhaul a month or so ago. For the past week, it has become completely unusable and a serious RAM/CPU hog.

    Disabling vp9 entirely did not resolve, updating to the latest release did not resolve, disabling all add-ons did not resolve, and YT runs smoothly in every other browser I’ve tried.

    1. Tony said on June 27, 2024 at 3:26 pm

      Timothy, you didn’t read the technical details of the bug. Had you actually done so, you would realize that this problem was entirely different than what you experience.

      Your issue is likely due to a garbage computer that you refuse to upgrade, or your internet is on the low-speed side. You can try to work around some of that by using an extension like ‘Tweaks for Youtube’, and have it set video resolution to a static like 720 or 1080. This bypasses the ‘Auto’ garbage that YouTube uses.

  4. Anonymous said on June 27, 2024 at 6:05 am

    Yeah, this is what you do when you develop a browser, you fix compatibility issues, especially if they are exclusive to ‘you’.

    Do you think other browsers will not fix their issues when their own features or ‘protections’ or whatever affect websites? it’s exactly the same, didn’t work in Firefox, Firefox fixes it, because Youtube just like any web developer can do whatever they want, and if it works fine in Chrome, then many will not check if it works in Firefox or not, and even then, they would have seen the video was ‘okay’ and call it a day.

    Look at tiktok, it supports Document PIP, which is exclusive to Chromium, just like Youtube, do you think they shouldn’t do that only because it is not compatible with Firefox or Safari? if it works in the engine most people use, then it is fine, and that’s exactly the same thing here, even if it was an ‘issue’, it was still exclusive to Firefox or non-Chromium browsers and that means, Firefox had to fix it and do what Chromium does or whatever.

    People crying because web devs can do whatever they want and they can’t see “oh videos are causing buffering in a browser that has 3% marketshare” (something they wouldn’t have noticed anyway, unless you are a firefox user) it’s just weird. People need to grow up and stop pretending Firefox with its 3% and declining marketshare is so much threat to Chromium browsers Youtube needs to ‘sabotage’ it… no that’s not it, it’s just Firefox having to fix whatever they are doing wrong or not doing compared to the one engine that matters.

  5. Stephen B said on June 26, 2024 at 8:03 pm

    Updated to 127.0.2 a couple of hours ago, made no difference. Between 90-100% of the YouTube videos will not play or even preview on my copy of FireFox. Sometimes refreshing the page will get a couple to play but most often not. No problems with Chrome but I just don’t like Chrome as I have been using FireFox since the second year it existed.

  6. Anonymous said on June 26, 2024 at 5:04 pm

    This is still not fixed in v127.0.2 and it is quite clear that google is doing this. STOP MESSING WITH THINGS GOOGLE

  7. Anonymous said on June 26, 2024 at 2:22 pm

    @Iron Heart
    you’re so damn optimistic

    1. Anonymous said on June 27, 2024 at 1:29 pm

      quiet you

  8. John said on June 26, 2024 at 1:00 pm

    It’s suspicious of course but every other browser worked fine except for Firefox even Safari worked and did not use Chromium and Firefox had to find a solution not YouTube. Leaves me skeptical that the Firefox team did not properly test a Firefox release.

    1. Herman said on June 26, 2024 at 4:23 pm

      Hah, just wait until Firefox and Manifest v2 compatible browser that support the full uBlock Origin feature set go extinct. Then the next target will be bullied into extinction by the “don’t be evil” tech bros in Mountain View.

      As the creator himself sayeth:

  9. BigG said on June 26, 2024 at 10:15 am

    Oh my! They had found a workaround or a fix, better come up with another one. ~Google.

  10. bruh said on June 26, 2024 at 10:10 am

    I am honestly amazed, until last week I used to use an older FF version, (from 2022), and I thought everything was fine – this week I got ESR 115.12.0 (didn’t overwrite the previous install, installed side-by-side) so I could use the “echelon” theme, and wow, the RAM usage has more than halved – I can only assume my previous firefox had a memory leak or something, as I was always in the 90% range on RAM usage (16 Gb).

    Don’t get me wrong vanilla firefox is a “flat” soulless disaster but under the surface clearly they’re improving lots of things.

    I never view videos in more than 480p so impossible for me to have noticed it, but the question is: how did this only affect firefox? If the error is from youtube’s side, and chrome miraculously handled it, that just seems suspicious.

  11. Iron Heart said on June 26, 2024 at 10:07 am

    The truth of the matter is that if you test against Chromium (Blink) and Safari (WebKit), you’ve already covered 97% of all visitors of your website already. This is true for every website out there. If you consider it like that, why would Google employees waste their time testing for a 3% market share engine (Gecko)? Would you like it if your own boss asked you to cover any and all edge use cases?

    Further, if it can be fixed on the Firefox side it could as well be described as a Firefox bug, alright? So blaming Google for it, given the fact that every other browser works find isn’t it. It is Mozilla’s responsibility to ensure their browser works with mainstream websites and not the other way around, they are in no position for the reverse to be true. This comment section needs a reality check, the replies so far are dreadful because they miss the point of their use case being an edge use case.

    1. NotOnMySideOfTheCloud said on June 26, 2024 at 10:30 pm

      “Edge” or not, I would think that discounting 3% of your already existing customers/clients/audience is not good for your bottom line as a business practice in the long run. Unless you think you can “edge” them out of any current or future association with any competition. Or you are just being plain arrogant–bad karma.

      It was not a bug in Firefox as it did not originate from them, nor was it due to breaking something that worked before. I think you are the one who needs a reality check.

    2. Anonymous said on June 26, 2024 at 7:32 pm

      didn’t read. get lost.

    3. Yash said on June 26, 2024 at 6:03 pm

      Peter Thiel bootlicker detected. Oh yes master let me assist you in your vulture capitalist dreams. I’m the privacy conscious Brave user here trashing Firefox while using a browser engine made from Google. Good job, go get a life now

    4. Herman said on June 26, 2024 at 4:24 pm

      Truth is, malformed stream packets are not an implementation according to spec.

      *drops mic and walks away*

      1. KyleG said on July 5, 2024 at 12:01 pm

        Whose specs? VP9 is a Google video codec and webm is a Google media container.They define the specs of their codecs and containers. Webm can handle bad stream packets according to the capabilities of the container. Google gets to decide what their codecs and containers can or can’t do. Chromium’s webm demuxer and ffmpeg’s webm demuxer can handle bad stream packets. So Firefox’s webm demuxer should do too.

  12. Manu B said on June 26, 2024 at 8:10 am

    LOL, User No. 5 is here (and I know of many more…)

  13. Bobo said on June 26, 2024 at 8:08 am

    Almost 6 months to fix this is quite alarming, and it took one smart enough guy and a bit of luck. Google have probably a whole team of dedicated Firefox assassins working full time on the next sabotage mission. At least we can now be sure that all future issues with browsing will be caused by Google, so thanks Google. Your special operation is out in the open. Let’s wait and see what the law has to say about this.

    1. Herman said on June 26, 2024 at 4:39 pm

      Plausible deniability is one hell of a way to force adoption of a browser the tech bros want you to use:


      I’m sure these are all spooks! Nobody would be this evil! Right..?

    2. Bobo said on June 26, 2024 at 11:33 am

      I will also add that the issue is NOT fixed completely, still major buffering issues in many vp9 videos at 1440p, so back to the drawing board Mozillaboys and gals. In the spirit of my previous comment, there’s also the fact to consider that Google’s Firefox assassin team are closely following the bugfixes at Mozilla so Google have most likely changed something again as soon as Mozilla rolled out this new version. I’m quite tired of this issue and the slow pace Firefox fixes these things, so I use FreeTube which works flawlessy for all my adfree YouTube needs. I will install FreeTube on my familys computers asap and will also recommend it to everyone I know and don’t know. F**k you, Google.

    3. John G. said on June 26, 2024 at 8:42 am

      After reading your comment, I agree that it’s suspicious enough this issue…

  14. Tachy said on June 26, 2024 at 6:25 am

    FFS Mozilla, do you know how long it took google to think that stuff up?

    Now they’ll have to create a new feature (bug) to thwart browsers that don’t share data with them!

  15. Winteriris55 said on June 26, 2024 at 6:00 am

    The 3 firefox users will be happy.

    1. Anonymous said on June 26, 2024 at 10:57 am

      Brave miner arrived.

    2. karlo2105 said on June 26, 2024 at 9:39 am

      I have been using Firefox since 2006 and I always install Firefox on computers when i am asked to provide help.

      1. Iron Heart said on June 26, 2024 at 10:08 am


        Congrats for widening the attack surface of these PCs in the name of installing a lackluster, irrelevant browser that doesn’t even work with the most mainstream of mainstream websites.

      2. Anonymous said on June 27, 2024 at 12:27 am

        Iron Heart,

        Google will never be your boyfriend.

      3. Jody Thornton said on June 26, 2024 at 11:56 pm

        Yes, I wish they would have fixed compatibility for Canada Life and YouTube on th ESR 115 version, which is SUPPOSED to be the long-term service release. So much for Mozilla. Maybe I need to look at putting Supermium on here.

      4. Brotherhood of Google Fanboys said on July 1, 2024 at 2:35 am


        Your unquestioning loyalty to Google does not go unnoticed. Welcome to the Brotherhood.

      5. traeh nori said on June 27, 2024 at 2:34 pm

        Supermium? If you are using Windows XP on the internet, then you have bigger problems than YouTube not working.

        Also Firefox hasn’t worked on Windows XP for years.

      6. Jody Thornton said on June 29, 2024 at 3:05 pm

        I don’t know if my last post went through, but my system runs Windows 8, and I’ll be moving soon to Windows 10 LTSC 2019, so I’m not in the least bit worried about XP compatibility.

      7. Jody Thornton said on June 29, 2024 at 3:03 pm

        I’m using Windows 8, and soon I’ll be moving to Windows 10 LTSC.
        Not worried about XP compatibility in the least.

      8. Herman said on June 26, 2024 at 4:41 pm

        TOR browser is pretty safe. Maybe the TOR project will one day fork a famous crypto bro browser as their standard. But I’ve not been drinking enough cool-aid to see that ever happen.

    3. Tom said on June 26, 2024 at 9:09 am

      There are more than 200 million (!) active (!) users (“sometimes users” not included). So you’re obviously a troll.

    4. John G. said on June 26, 2024 at 6:59 am

      User number four here!

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