YouTube uses lower quality options on browsers running on Arm-based systems — misreporting as an x86 CPU appears to be a widespread browser fix

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Firefox on Linux appears to get punished for truthfully reporting 'aarch64' on Arm.

Apple Silicon is sad
(Image credit: Apple)

Linux developer Hector Martin has discovered that YouTube is "deliberately crippling Firefox on Asahi Linux." Martin, also known by the handle Marcan, says YouTube downgrades the video quality and resolutions served to Firefox users on Macs with Arm-based systems, at least when they're not running MacOS. This behavior is particularly galling as Arm-devices can be very powerful in 2023. Asahi Linux, for example, is a project responsible for porting “a polished Linux experience” to Apple Silicon (Arm CPU architecture) Macs.

Marcan confirmed his YouTube downgrade on Arm hunch by changing the browser user agent (UA) and doing some A/B testing. After changing the Firefox UA parameters from ‘aarch64’ to ‘x86_64’ he says "suddenly you get 4K and everything!"

Digging a little deeper, Marcan checked the code that was responsible for the Arm reaction. He noted that YouTube would serve 1080p videos by default to x86_64 machines. However, the default for Arm devices was a mere 240p. Marcan reckons what he observed is an outdated bias, given the plethora of multi-core Arm processors in modern devices.

One of the reasons for the bias might have been uncovered, though. "YouTube thinks aarch64 Firefox is... a HiSense TV?!" noted the developer — specifically a HiSense 65a67gevs. YouTube doesn’t allow the option of 4K playback on this TV for some reason.

With the YouTube / Firefox on Arm relationship analyzed, Marcan wondered what Google's own Chrome browser was doing when running on Arm hardware. He found a surprising little Google hack: "Chromium on aarch64 pretends to be x86_64." Thus, YouTube playback in Chrome using Asahi Linux defaults to 1080p playback and can be nudged to 4K.

Firefox outfoxed

(Image credit: Hector Martin)

After verifying his observations, Marcan decided to act on what he discovered. He filed a bug report with Mozilla, with the hope of getting Firefox updates to "report bull**** architectures." Marcan also decided to add some workaround code to Asahi Linux.

There's some follow-up discussion below the source report on Mastodon and the Hacker News site. Some early comments thought it was reasonable that YouTube defaulted to 240p on Firefox / Arm. However, it was pointed out that the change of UA also facilitated 4K playback, which was not an available option on Firefox + Linux + aarch64. Another interesting comment noted that Firefox, Chrome, and Safari on modern MacOS (running Apple Silicon) all have the UA set "incorrectly" to x86_64 by the developers. Thankfully, it's pretty easy to change your browser UA information, so you can set it to whatever you want to see what benefits may be available.

YouTube has had more than its fair share of headlines recently. It recently started aggressively checking for any kind of browser and extension-based ad-blocking. Not long after YouTube scripts were propagated to do this spying, a privacy consultant based in Ireland decided to file a criminal complaint.  Also, last month Google was alleged to be crippling Firefox's performance by implementing video loading delays. YouTube released a statement in response to this accusation, but sadly the response seemed to be answering a question that hadn’t been asked — something about ad blockers. A UA switcher was again an easy solution to the issues observed.

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Mark Tyson
Mark Tyson
News Editor

Mark Tyson is a news editor at Tom's Hardware. He enjoys covering the full breadth of PC tech; from business and semiconductor design to products approaching the edge of reason.

10 Comments Comment from the forums
  • Amdlova
    On the s23 and A54 use the brave for see youtube for a long time. but can't do full screen on videos.
    kinda of bugged. Because google try'n force you to use own application.
    Reply
  • Co BIY
    I also can't get oil filters at Walmart for my 1988 Yugo.

    This is what happens when you are very outside the mainstream.

    You get to feel unique and cool but there are costs.
    Reply
  • digitalgriffin
    Arm architectures are usually reserved for low power devices like tablets and phones, where battery life is sensitive. There are so many ARM based chips, it's hard to say if certain combo is ( chip is particularly power efficient at 4k av1. Heck,early rasp pis had poor fp performance and horrid java support. So I could understand it taking the safe route if it's not known the particular architecture (hardware and software) supports it.
    Reply
  • thestryker
    It's one thing for the default settings to be different, but arbitrarily locking out settings entirely seems dumb.
    Reply
  • drajitsh
    How do you change the user agent on Firefox on Android?
    Reply
  • NinoPino
    Co BIY said:
    I also can't get oil filters at Walmart for my 1988 Yugo.

    This is what happens when you are very outside the mainstream.

    You get to feel unique and cool but there are costs.
    But modern Macs are not like a '88 Yugo.
    Reply
  • Darkoverlordofdata
    Where are all these Arm's that are so powerful? I tried this trick on both my Lenovo Chromebook and my rpi4. Both Suck, and had to revert. More B.S. from Tom's Hardware.
    Reply
  • HaninTH
    ARM is trash for a lot of things, but video playback isn't one of them. Defaulting options is one thing, but not allowing any other choice is ridiculous. To then have the trigger for this lock being something that is easily countered is proof this move is short sighted.
    Reply
  • TJ Hooker
    Note that the developer on Mastodon believes this issue only occurs if you're using software decoding.

    It does seem plausible that this was just some lazy heuristic implemented years ago. Which would have made some sense at the time, as most ARM chips were relatively slow and probably would have performed poorly trying to decode high res video in SW. As that changed over the years, everyone else just worked around it (by spoofing UA or whatever), and that increasingly obsolete heuristic never got updated. The fact that higher resolutions were blocked altogether, rather than simply not being the default, is suspicious though.

    It seems unlikely that Asahi linux was specifically targeted. Some of the commenters on Hacker News mention then Asahi devs have a reputation for being... dramatic.
    Reply
  • DingusDog
    Meanwhile I'm over here YouTubin' on Chrome with RTX Video Super Resolution.
    Reply