Stripping the _gl Parameter

My very first day on the job: adding one line to strip Google Analytics linker parameters from copied URLs.

Bug 1947168 | D271523 | Reviewer: manuel

The Problem

When you copy a URL from a website that uses Google Analytics cross-domain tracking, the URL often contains a _gl query parameter. This parameter carries a visitor identifier that follows the user across domains. When someone copies and shares that link, they’re unknowingly sharing a tracking token.

Firefox’s “Copy Clean Link” feature strips known tracking parameters when you use the clean copy option. But _gl wasn’t on the list.

How Copy Clean Link Works

Firefox maintains two JSON files that define which query parameters to strip:

• StripOnShare.json (MPL2 license) contains global parameters and site-specific rules
• StripOnShareLGPL.json (LGPL license) contains rules derived from community lists

The global.queryParams array in StripOnShare.json lists parameters that should be stripped from all URLs, regardless of the site. This is where UTM parameters (utm_source, utm_medium, etc.) already lived.

The Fix

One line:

{
  "global": {
    "queryParams": [
      "_gl",
      "li_fat_id",
      "utm_ad",
      "utm_affiliate",
      ...
    ]
  }
}

Adding _gl to the global list means it gets stripped from every URL, on every website. This is the right scope because the _gl parameter is always a Google Analytics linker token, regardless of which site it appears on.

What I Learned

1. Small patches can have outsized impact. This is one line of JSON, but it affects every Firefox user who copies a URL from any site using Google Analytics cross-domain tracking. The simplicity of the fix belies the scope of the improvement.
2. Open source onboarding is real. This was my first Phabricator diff, my first review cycle, my first encounter with ./mach lint. Having a simple, low-risk patch as my first contribution let me focus on learning the process rather than wrestling with complex code.