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About Spectator

Spectator is a Firefox extension that collects data about how Firefox is used. This information is used to better understand what people value in the browser. The extension is now available from AMO.


The Spectator extension collects usage information about the browser.

What can Spectator collect?

Right now we are taking a snapshot of your profile (extensions installed, screen resolution, arch, installdate, etc... NOT history) every time you open the browser, logs all UI interactions, and log how/when documents are loaded (typed, link, etc). See full technical details here. But don't be scared, keep reading....

Can you see what websites I'm going to?

No. The only URIs we capture are chrome document loads. Also, any string that comes from the user (a ui event name, an extension name, etc) is one-way hashed (md5) client side. This way we can only see data we already know about.

If you can't read what is being sent to back, how is it helpful?

Consider "Browser:Reload". In this case, the string "Browser:Reload" is hashed and then sent back to mozilla ( "fgKIKfJEiGq5arJfJCcOSQ==", base64). On the server side, we can hash the common stuff (like "Browser:Reload"), and connect the dots. Or consider a custom extension. If you're writing "super-secret-extension-1337", we have no idea what it is called, so we will not be able to resolve the hash. However, if you publish it on addons (or some other place we can find it), we have the extension-ID and can generate the md5.

Can I see what you have collected?

Yes. You can see what has been collected since the last upload interval. To do this, hit: about:metrics, you will see the XML file we have collected since you last uploaded the data to mozilla. If you're very clever, you can make a snapshot of the data before it gets uploaded by copying it out of your profile. It is called metrics.xml.

How do I know it is working?

Hit about:metrics and see if there is a log. If you do not see any XML kick the browser once. If it is still not working, let me know!

What is mozilla going to do with the data?

We hope to use it to make Firefox better. For the first time, we'll be able to see how the user interacts with the browser. We'll know how many extensions people use. We'll be able to track if that fancy new star gets any action. From the 3 users we already have, we can say that the most common UI Event sequence is "close a window then open a tab". Lets use that info to make the best "close a window and open a tab" experience in the world!

Can I disable collection?

Yes. You have three options:

  • Un-install or
  • Disable or
  • Toggle the add-on pref

However, the easiest way is to not install the extension in the first place!

Where can I file bugs?

Toolkit, Data collection/metrics

Technical Implementation

Please see Browser Metrics for details regarding the technical implementation.