What Version of Firefox Do I Have

What is What Version of Firefox Do I Have?

Reads the Firefox version straight out of your browser's user agent string, a quick check without digging through the hamburger menu → Help → About Firefox. Useful when you need to confirm compatibility with a site, report a bug against a specific build, or check whether an extension needs a newer release than the one you're running. The check runs entirely in your browser: nothing about your version or user agent is sent to a server. That also means it's only as reliable as what Firefox itself reports. Modern Firefox still exposes its full version by default, but that could change as browsers move toward more privacy-preserving user agents, the way some other browsers already have.

How to Use This Tool

1. 1

   Open This Page in Firefox: Visit this page in the browser you want to check.

2. 2

   Read the Detected Version: Your Firefox version, parsed from the user agent string, appears automatically.

How It Works

Firefox includes a `Firefox/XX.X` token near the end of its user agent string, and this tool looks for that specific pattern in `navigator.userAgent` and reads off the version number. It's parsed entirely client-side; nothing is sent to a server.

Why This Might Be Wrong or Say "Unknown"

If you're not on Firefox, there's no `Firefox/` token to find, so the tool reports it isn't Firefox rather than guessing. If you are on Firefox and still get an unexpected result, the likely causes are: your browser (or a privacy extension) is deliberately sending a generic or modified user agent, which is an increasingly common privacy practice across browsers generally even though Firefox itself hasn't historically frozen its own version this way; you're inside an in-app browser embedded in a social media app, which often substitutes its own limited user agent string; or the user agent is otherwise spoofed for compatibility with a site that checks browser identity.