Telemetry Status

Telemetry Present

Telemetry infrastructure has only been deployed for week, but we are already gathering interesting data:

  • Memory usage from about:memory gives us an idea of what constitutes typical memory usage for Firefox
  • Cycle-collection overhead, stats tell us about browser pauses due to memory cleanup
  • Detailed startup profiling tells us whether our new library preloading logic is effective
  • Info on whether the browser was shutdown correctly will help us diagnose shutdown problems
  • Plugin enumeration timing to make sure my faster plugin enumeration stays fast
  • HTTP connection profiling to help optimize page loads

Since the branch point for Aurora is approaching in less than a week, I don’t expect many more probes for Firefox 7.

Telemetry Future

One problem with doing awesome optimizations that as code changes, they frequently get accidentally undone. I plan to add telemetry to keep tabs on every significant optimization that I do in the future, in addition to retroactively adding it to the past ones. I expect other Mozilla developers to do the same.
In addition to keeping tabs on Firefox performance, we can also learn about JavaScript feature adoption, the kind of hardware (and OS) that users run Firefox on, etc to better match users’ needs.


  1. The cycle collector count probes have landed on inbound! Hopefully they’ll make it in to 7.

    In terms of JS feature adoption, it would be fairly easy to add a count of how many WeakMaps there are, as the JS GC builds a list of them every time it runs. That’s kind of a bleeding-edge experimental feature, though.

  2. Telemetry is great news. It is also incredibly overdue. To think that browsers have existed in the mainstream for at least 15 years and performance has always varied, only now is Mozilla finally getting real-world performance data from users? Too bad this wasn’t ready for Firefox 4. It could have helped point out the terrible memory problems much sooner. As it is we have to wait until Firefox 7 before they are resolved 🙁

    Keep up the great work Taras.

  3. @pd
    It’s a little embarrassing I admit. As I mentioned before in other posts, having a limited number of people means you can’t do all cool/useful projects.
    A second reason is that as a project we are really against collecting any more than a bare minimum amount of info on our users (the opposite of certain big web advertising firms). Too sensitive in this case.

  4. Did it really go into Aurora 6.0a2 from two days ago ? I don’t see the option in “Advanced/General tab”.

  5. working in Seamonkey 2.4a2

  6. @jmdesp, yes it went into Aurora, but you have the old version. Correct version is 7.0a2

  7. working in Seamonkey 2.5a1, after rdf edit

  8. if you add that much telemetry and more in the future there’s the possibility that it may slow down instead? is there an option not only to not send data but also to not do telemetry at all?

  9. @AV. There is no slowdown, no matter how much telemetry we do. We will only measure “cheap” things with it.

    Currently telemetry-metrics gathering code is disabled immediately after startup if do not opt in.

  10. thank you for the fast reply, I was afraid for my little netbook

  11. Just got the new FF7 and I was eager to try the telemetry, but I’m extremely annoyed to see lousy validation in place, probably as a side effect of hiding the http:// part.

    Go to the URL bar, and type “h” – IT GETS REPLACED with “f” – extremely annoying. Thus, I wanted to search my history for either “hudson” or “honda” but I get “fonda” – nothing found.
    Please do something to fix that stupid validation.
    Also, the Panorama windows are one over other, totally mis-aligned.

  12. @Kiril Varbanov
    Not happening with me. Check for addons maybe? FF7 Arch Linux