Firefox has become inordinately slow starting YouTube videos

Since the latest Firefox update to 121.0.1, it seems to have become very slow in starting to play videos and streams, often taking several seconds before showing anything other than a black rectangle. Additionally sometimes when I scroll down to the comments or chat and then back about half the image (depending how much was hidden) remains as white for an appreciable time.

Usually once it gets started it plays OK, though occasionally it can be stuttery early on.

Running up-to-date Manjaro Plasma (X) stable.
Graphics:: free drivers, hardware:

01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Lexa PRO [Radeon 540/540X/550/550X / RX 540X/550/550X] (rev c7) (prog-if 00 [VGA controller])
	Subsystem: Sapphire Technology Limited Lexa PRO [Radeon 540/540X/550/550X / RX 540X/550/550X]

CPU: 6 × AMD Phenom(tm) II X6 1055T Processor
16Gb RAM
Kernel: 6.6.10

Network: 2Mbyte/s download ADSL.

you think it’s related to this?


I have YT Premium so it shouldn’t (but there again, it is Google at the back of it).

For the record. Are you using any ad blockers in Firefox?

uBlock Origin (recommended) or Ad Block, for example?

Even with uBlock Origin, I’ve noticed lately that I must click the video container before it will play (only an empty black void is displayed otherwise. I imagine the use of other ad blockers might reveal even greater annoyances to the YouTube advertising experience.

I use AdBlock Plus

Remove it (you can always add it again later).

First, see how YouTube performs without any ad blocker at all. Then try uBlock Origin (with default settings) and again, see how YouTube performs.

For best results, perform these tests both when logged into YouTube, and when logged out. Close and reopen your browser each time. Cheers.

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in this Reddit thread people with Premium also experience it.

While this remains a possibility, I’ve now had a chance to check the performance of my “media box”, which is a much newer machine (actually I’ve only had it a few days).

CPU: AMD Ryzen 5 4500 Six Core CPU (3.6GHz-4.1GHz/11MB CACHE/AM4)
Video: 2GB NVIDIA GEFORCE GT 1030 - DVI, HDMI (proprietary drivers)

Otherwise similar specs 16GB, Manjaro KDE , but connected by WiFi rather than Ethernet to the same router.

On that machine there is very little delay (no more than a second or so to start the same streams).

Makes me wonder if the current build of Firefox is not optimized for the 12 year old CPU.

[Might also be worth checking the old media box which is Intel and even older, but I won’t have time to do that till the weekend].

Its at least a problem.

  • Its much more resource hungry than alternatives.

  • Allows ‘acceptable’ ads by default

  • Has working relationships with advertisers

  • Less performant than alternatives

  • Relies more on cosmetic filters than alternatives

  • Does not actively develop with community input to evade anti-adblock


I’d switch it out for ublock origin if I were you.

See, ex,

Back to general performance … you might want to double check hardware acceleration… as well as note that current mesa has had certain proprietary bits removed … which could negatively impact amd users … especially those that would have relied on the more dated formats like h.264 .

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Thanks all. Using ublock origin improves things to an acceptable level.

Still a bit of a puzzle why the other box wasn’t dragged down by AdBlock plus (maybe there’s an H/W issue there?)

Didn’t I already suggest uBlock Origin? Yes, I think I did.

My short answer to that is that it’s all FUD and prejudice. Let’s go over your arguments one by one…

I haven’t noticed any of that, and I’m not exactly running the latest & greatest hardware here. This is a 6-core Intel i5-8400 — real cores, no Hyperthreading™ — with 16 GiB of RAM, about 512 MiB of which is used by the integrated Intel 630 UHD GPU.

Which can be disabled with a few simple clicks.

Not in my experience.


At this point in time, I am not seeing any ads or experiencing any slowdowns with AdBlock Plus in Firefox.

However, I am using the same AdBlock Plus in Chromium, and in Chromium I am effectively seeing static ads on YouTube, and remnants of ad videos before the main video starts playing, as well as that YouTube does indeed work slower there. And this all started after the most recent update to chromium.

So in my book, Chromium is what’s causing the problem here on my computer, which makes sense, given that it’s a Google product. At the same time, I am not getting any problems at all in Firefox, which clearly exonerates both Firefox and AdBlock Plus.

That all said, I do not know why the OP is having those problems, but it may be down to one of his other browser extensions, and it’ll definitely be related to Google/YouTube’s attempts at cracking down on ad blockers.


Both OP here and any unbiased metric I’ve ever seen shows obvious differences in both resource usage and effectiveness.

You can keep disagreeing and seeing ads :person_shrugging:

I thought I had made it abundantly clear that I am not seeing any ads in Firefox — I am however seeing them (and/or remnants of them) in Chromium.

I do not know anything, but you could also read:

Except I dont get them in chrom*.

Also see any testing like here:

But we’ve gone over these things before and it amounts to this information being useless … so I dont see the point of the discussion.

I tried to read that, and still don’t know anything. The site was too interested in setting my permissions, and signing up, which ultimately bypassed whatever the intended link might have been. :wink:

In short:

YouTube’s performance issues with Adblocker / Plus could be due to a bug in Adblocker. This was particularly analyzed by Raymond Hill, the developer of the competing ad blocker uBlock Origin, in an X post.

ABP had a performance issue with a recent version
also linked in the German article above.

I experience this with Firefox anda Google Chrome both on Win 10 and Manjaro Xfce.
I only use UBlock and go to his site to see if it’s update do YT ads:

At the time of this post it was not updated yet:

Sometime YT says I don’t have an internet connection (when I have) and I have to reload.

Google has to be put in order…