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Telemetry and User Control: FAQ

What is Telemetry and why is it good for Firefox users?

Telemetry is a Firefox feature that collects valuable engineering data about the browsing experience in order to make Firefox perform better. Telemetry measures and collects browser data such as performance, hardware, usage and customizations. This data, used in aggregate, allows Mozilla to identify new issues and regressions, obtain more specific information about problem areas in the browser, and, as a result, provide a better browsing experience.

Telemetry may also enable experimental Firefox features from time to time.

What kinds of data does Telemetry send to Mozilla?

Telemetry collects information about your Firefox browsing experience to improve Firefox features, browser performance and stability. Examples of the kind of data Telemetry sends to Mozilla includes start-up time, time between cycle collector runs, memory heap used, whether hardware graphics acceleration or Java is enabled, and more.

Telemetry does not collect any bookmarks or passwords. It may collect anonymized site visit information in some circumstances, such as when a secure browsing connection fails to connect, or for some experiments.

What are the privacy implications with Telemetry?

Mozilla takes user privacy very seriously. More information about our privacy practices can be found here:; and in our Firefox Privacy Policy here:

How do Firefox users enable/disable Telemetry?

Enabling and disabling Telemetry is easy. Instructions can be found in the support articles for Firefox for Windows, Mac and Linux and Firefox for Android.

Why is Telemetry enabled by default on the Firefox pre-release channels?

Users use Firefox pre-release builds in order to test and provide feedback on new features; enabling Telemetry by default on these channels makes it easier for them to do so by allowing Mozilla to better identify new issues and regressions early in the development cycle and make Firefox a better product. Users can choose to disable Telemetry at any time. See How do I enable/disable Telemetry data collection?.

Is Telemetry enabled by default on normal Firefox releases?

No. Users of Firefox release builds must explicitly opt in to Telemetry.

Can Firefox users change their mind and enabled/disable Telemetry later?

Yes. Users can enable or disable Telemetry data collection at any time. The change will take immediate effect. See How do I enable/disable Telemetry data collection?.

Can Firefox users view the data that Telemetry collects?

Yes. When Telemetry is enabled, the about:telemetry page in Firefox provides the ability to view all of the data measured and collected from the browser. Type about:telemetry into the URL bar in Firefox to view this page.

How does Mozilla use the data that is collected?

The data measured and collected by Telemetry allows Mozilla to identify new issues and regressions, obtain more specific information about problem areas in the browser, and, as a result, provide fixes for rising problems more quickly. With this, the Firefox engineering team looks to answer these types of questions, among others:

  • How long does it take Firefox to start?
  • How long does it take Firefox to load a web page?
  • How much memory is Firefox consuming?
  • How frequently do the Firefox cycle collector and garbage collector run?
  • Was your session successfully restored when you last launched Firefox?

How have you acquired product-related data in the past to help improve Firefox?

Firefox users can enable some data gathering tools, like TestPilot, that carry out specific tests on parts of the code base. The Firefox ‘Help’ menu also offers users a chance to submit written feedback about their experience with Firefox that goes directly to our customer support team. Firefox also periodically checks to see:
a) whether there is a newer version of Firefox to upgrade to, and whether the computer is signed up for automatic updates.
b) whether there are any harmful or outdated add-ons or plug-ins installed that Firefox should disable (e.g., when a plugin causes Firefox to crash on startup or contains a critical security vulnerability).
Finally, we have a crash reporting feature that, when the user agrees, sends technical information back to Mozilla if a crash occurs. More information about Mozilla’s data practices regarding Firefox can be found in the Mozilla Firefox Privacy Policy.
Over the years, Mozilla has relied on various combinations of the above data to determine the number of installations of Firefox and try to identify usage patterns or correlate performance issues with changes in these data types.