Mozilla is investigating huge Telemetry performance issues in Firefox for Android

Martin Brinkmann
May 30, 2024

Mozilla, maker of the open source Firefox web browser, has launched an investigation to analyze the impact of Telemetry on the browser's performance on Android.

According to the initial report, Telemetry is causing huge overhead in Firefox for Android. This impacts the loading of websites, but also the browser's startup.

A test on CNN, for instance, concluded that Telemetry was adding 16.5 seconds of extra CPU time to the loading of the site.

Mozilla writes: "This means that device disks are getting hammered with writes on all occasions: page load, scrolling, video playback, startup. For example, we have observed hundreds of writes per second during scrolling (before bug 1898515 turned off the metric that was causing most of these updates) and ~32000 writes while loading On the Pixel 6 we were testing on, each write took around 0.5ms of CPU time, so that comes out to 16.5 seconds of extra CPU time for loading"

On browser start, Firefox would use 40% more CPU time when compared to a version of Firefox with Telemetry set to off (35 seconds of CPU time compared to 25 seconds of CPU time).

This happens in Firefox Nightly as well as the release version of the web browser.

Mozilla discovered why Telemetry is adding the overhead to the browser. The core reasons are that writes to the Telemetry database are not grouped and that the entire database gets "serialized to disk" whenever it is updated.

In short, whenever new metrics come in, they are written to the database and the database is serialized to disk.

In other words, whenever Telemetry is updated, it is written to disk immediately. Since Telemetry is collected widely when enabled, it impacts the browser's startup, the loading and use of websites, media playback and other areas significantly.

While Mozilla is investigating the issue, Firefox users on Android may want to disable Telemetry in the browser to speed it up significantly.

How to turn off Telemetry in Firefox for Android

  1. Open the Firefox web browser on the Android device.
  2. Select Menu > Settings.
  3. Open Data collection under Privacy and security.
  4. Set Usage and technical data to Off.
  5. Set Marketing data to Off.
  6. Set Studies to Off.
  7. Firefox displays a prompt to restart the browser.

Recheck the menu to make sure that Telemetry is turned off. Note that Firefox is one of the few browsers that lets users turn off Telemetry comfortably in the settings.

Do you use Firefox on Android? 

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Mozilla is investigating huge Telemetry performance issues in Firefox for Android
Mozilla is investigating reports that Telemetry is causing performance issues in Firefox for Android.
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  1. Anonymous said on June 17, 2024 at 1:48 pm

    the new firefox stops all adds and it will not let you install any of them at all

  2. Johan said on June 5, 2024 at 12:15 pm

    On the new linux 6.8 kernels and radeon drivers, pink artifacts are created on youtube videos.

  3. upp said on May 31, 2024 at 10:58 am

    > Firefox, which is already 2-3 times behind Chromium, is very difficult to survive.

    Saying this without anything to back it up, at least show some benchmark, but I doubt lamo even recent benchmark is showing Firefox is as fast or about 20% worse in terms of scoring.

  4. weird al said on May 31, 2024 at 8:21 am

    Disabling telemetry is the first thing I do when installing any software, driver or framework (including browsers, dotnet, nvidia etc). I don’t need any outdated fork with unpatched security vulnerabilities just because you can’t find the telemetry menu, FF works just fine.

    1. jo said on June 1, 2024 at 1:46 pm

      You don’t “disable telemetry” in FF, you twiddle a request toggle for some of it, often bypassed/disregarded. You politely ask the fox who works for daddy google and meta etc etc to stop unpolitely abusing and mocking you, again.

      You’re strangely appologetic to a repeat offender and quite disrespectful to its victims, you effectively called users stoopid for being abused with telemetry again and again. Does twiddling those toggles after more abuse every few weeks give you a dopamine hit? self-aware much?

      I don’t think “huge telemetry performance issues” means “everything is fine” eh.

  5. Rex said on May 31, 2024 at 12:57 am

    Gotta love the Mozilla masochists still crying about their travesty of a browser or trading tips on how to disable the latest idiocy that has no business existing in the first place in a browser that continues to be hyped as privacy friendly.
    Iceraven on Android strips out all telemetry and has supported more extensions since long before Mozilla belatedly brought them to their mobile browser.

  6. Tony said on May 30, 2024 at 11:35 pm

    Firefox DNS lookups are slow on Android, even with Telemetry turned off.

  7. Anonymous said on May 30, 2024 at 9:23 pm

    Telemetry is important, but obviously it shouldn’t affect performance.

    I don’t get how Mozilla didn’t notice this in Nightly and it affects stable too, like they should have seen in their dashboard performance stuff, if there was increase in CPU or Memory and then do something about it when they see it is the telemetry… like not push it to stable.

    Seems like Mozilla people didn’t care and now they are finding excuses to justify why they didn’t fix the implementation of telemetry before it was pushed to Stable or before adding more telemetry would cause performance issues.

    Well, this is why Mozilla is a weird company and their browser is losing marketshare, people can see these things, how weird their development teams are when they can’t see this simple thing way before it caused issues.

  8. John G. said on May 30, 2024 at 7:14 pm

    Google’s telemetry is the worst and… OMG, the article is about Firefox for Android! Thanks anyway! :]

  9. ILoveBraveBrowserJKLOL said on May 30, 2024 at 3:47 pm

    Lol y’all nerds need to chill. This is a minor blip. Once Mozilla figures this out they will be putting Chromium based browsers to shame in terms of performance. It’s going to be absolutely nefarious. Just wait.

  10. Anonymous said on May 30, 2024 at 2:24 pm

    firefox can’t be fixed if they don’t remove ai because that is the cause of slow net slow load and slow loading web pages ai is the cause go block ai in firefox and it will stop being slow

    1. Tom Hawack said on May 30, 2024 at 4:11 pm

      There is no AI in Firefox, at least for the time being. Maybe had you in mind telemetry rather than AI?

  11. Someone said on May 30, 2024 at 1:33 pm

    Or use Mull where all telemetry is removed.

    1. Dennis said on May 30, 2024 at 10:31 pm


  12. Tom Hawack said on May 30, 2024 at 11:54 am

    Why telemetry to start with? Officially to improve the application on the ground of users’ experiences. In my experience official statements, if true, may not be true till the end. I ban all telemetry, and when it comes to Firefox, fortunately prefs allow to do so. So why not just do it ? I’m referring to Firefox for Windows, no idea of a user’s ability to block telemetry on a smartphone.
    Telemetry, telemetries everywhere. “We’re not tracking you, not even following anything you do, we’re only recording anonymous data your use of our software provides”. OK, then forgive my suspicions but, hmm, I’ll stick to them if you don’t mind.

    1. Allwynd said on May 31, 2024 at 5:50 am

      Because they are selling it to Google and others to stay alive. If they stop doing it, they go bankrupt, not that they will be missed.

    2. Bobo said on May 30, 2024 at 2:21 pm

      They need telemetry to see what’s wrong with telemetry. Like putting crap in your boots so you can investigate why you have crap in your boots.

      1. Tom Hawack said on May 30, 2024 at 4:12 pm

        LOL. Nice one, @Bob :)

  13. bruh said on May 30, 2024 at 11:19 am

    “This means that device disks are getting hammered with writes on all occasions”

    There are no disks of any kind in a mobile phone, it’s a small thing but an annoying thing.

    Classic shooting yourself in the foot moment.

  14. Mystique said on May 30, 2024 at 11:09 am

    Anybody with any sort of intelligence is aware the telemetry will be NEEDLESSLY taking up valuable resources be it CPU, Bandwidth, Memory or otherwise in the background.
    The distinction between Telemetry and Spyware is essentially nonexistent. Telemetry is just the new name for spyware something my generation swore to destroy meanwhile idiotic companies felt that telemetry was a far better way to supposedly gather valuable data to allegedly improve the experience but taking away the obvious scumbaggery of this affliction it took away from the community interaction and involvement in products… the human touch which also fostered a fertile environment for innovation and development.

    Mozilla used to be thriving and now the community aspect is far far smaller. There are still some great people around but they are very much reluctant to get involved anymore.

    Chromium is straight up the product of modern day internet vommit that is founded on such principals of telemetry and garbage peddled by the advertising company Google.
    Mozilla is now in the middle ground of this.

    I am a firm believer that Mozilla needs to focus on going back to its root and opening up its extension system to support more api’s and allow use to have far more control. Being able to change the interface on Firefox was far easier back in the day and now its a mess that is easily broken after a simple update.

    Quit with the telemetry and go back to valuable human interaction. This way you may even indirectly encourage those users to become developers as they work with you to solve problems and innovate. This is what extensions were able to do also.

    When it comes to android every app you install from the google playstore has some sort of telemetry such as google analytics, Firebase, etc Some have many more than one so if you add that on top of the garbage that is already baked into the software also as is the case with firefox then you are really asking for trouble.
    You should be downloading or learning to strip out this garbage from many android apps as it is.

  15. Bobo said on May 30, 2024 at 9:44 am

    Yeah, that will probably need some fixing. While you’re at it make the damn app open with a clean slate and not the last visited site thank you. No, I don’t want to open the menu and scroll down to “Exit” every time I close it for it to do so. Also, I want to put all my bookmarks as a grid on the starting page. Not 4 or 5 bookmarks, more like 50 or 60, and I don’t want a stupid PIN icon on them either. Oh and I want to rename them myself and I demand that their icons don’t disappear if I delete my history, cache and cookies. Kiwi gets all this right, that’s ONE guy in Estonia with very limited resources. ONE guy. You have a GAZILLION dollars Google pay you every year and you can’t do anything right. Maybe you bought Pride flags for all the cash and went on a parade to save islam from the horrors of the western world.. The only good thing about Firefox on android is that you can use extensions, besides that it’s a mediocre browser at best.

  16. Husk said on May 30, 2024 at 7:58 am

    Firefox needs to focus more on performance issues. Microsoft is experimenting with a new interface on Edge, and this is probably the first time a company other than Google will decide on the overall design. In the face of this performance increase, Firefox, which is already 2-3 times behind Chromium, is very difficult to survive.

    1. Herman Cost said on May 30, 2024 at 2:01 pm

      I’m running Firefox on a 4 year old mid-priced desktop with about 15 extensions and various other tweaks, and I don’t have any perceptible performance issues (if there are imperceptible performance issues, that is fine by me). I can’t compare it to Chrome because I don’t ever use it, but on my setup the speed seems equivalent to Edge or Brave, and is clearly faster than Vivaldi or Pale Moon.

    2. Tom Hawack said on May 30, 2024 at 12:05 pm

      Performance and interface are two different things (unless to consider the impact of an interface on a user’s “productivity”, a term I hear everywhere and start to be fed up of).

      Performance ? Firefox runs fast here, 60+extensions, scripts, heavily tweaked (code and graphics), never encountered a velocity laziness.

      Interface ?
      > ” In the face of this performance increase, Firefox, which is already 2-3 times behind Chromium, is very difficult to survive.”
      I linger to understand the correlation.
      “2-3 times behind Chromium” ? Two or three, may 2 and a half ? In what terms ? general perception ?
      Love is blind, or not understandable as it seems.

    3. bruh said on May 30, 2024 at 10:48 am

      luckily you don’t need the latest interface to use a browser?

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