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To better discover errors in our software, Nightly collects data about JavaScript errors thrown from the browser chrome, or the user interface for the browser itself. These are not errors with webpages, but with Firefox itself. We collect these errors so that we can more quickly notice, diagnose, and fix issues in Nightly before they reach Firefox Beta and release Firefox.

Helpful Links

Access to Collected Errors

Error collection is currently a prototype
The Sentry project currently being used will be removed sometime in mid to late 2018.

Because errors may contain personally-identifiable information about users, access to them is restricted to approved Mozilla employees.

If you are an employee of Mozilla who wishes to access this data:

  1. Open the following bug template: Browser Error Access Request Template
  2. Replace in the bug title AND the summary with your LDAP email address.
  3. Read through the summary before submitting; it contains guidelines that you are agreeing to in order to access this data!
  4. Submit the new bug.
  5. After filing the bug, NEEDINFO [:Osmose, :mkelly] for approval. Once approved, ops will grant you access.


We use Sentry as the backend for collecting and aggregating errors. Sentry has a documentation site that explains some of their app's features.

Firefox-specific Search Filters

Errors in Sentry have several tags with metadata about the error that can be used in search queries:

"True" if the error was thrown from a moz-extension:// path, "False" otherwise.
Contains the AppBuildID of the Nightly build that threw the error

UI Improvements Extension

There is an extension available for users with access to the Nightly JS Errors project in Sentry that improves the UI specifically for that project:

  • Adds a "File Bugzilla Bug" button to the UI that opens the form for filing a new Bugzilla bug in the Firefox::General component. The form is pre-filled with details from the Sentry event being viewed, including the stack trace and error message.