Published at: Mar 2, 2026
One of the most popular parts of whatismybrowser.com is the feature that tells you if your web browser is out of date. It either confirms that your browser is safe and up to date, or it provides clear instructions to help you update to the latest version.
Normally this feature works very well; however in the case of the Extended Support Release of Mozilla Firefox, we are not able to give you accurate information about whether your copy of Firefox is up to date or not. The reason for this is that when you use Firefox ESR, it doesn't tell our servers if you are using the ESR version or if you just have an older, out of date version of Firefox.
In other words, from a browser-detection perspective, if you are using Firefox ESR, even though you're running a browser that is still maintained by the Mozilla team, your system still appears as if you're running a version of Firefox that is a few major versions out of date.
So we can't conclusively tell you if you're up to date or not, and as a result, it can be a bit confusing for people running Firefox ESR and are up to date to still see a "You are out of date" message. So, we have directed you to this page to explain. If you'd like to confirm that your browser is up to date, you can still follow the same instructions to update Firefox. It will either alert you that there is a new version of Firefox ESR available or it will confirm that your copy of the Extended Support Release of Firefox is up to date.
We hope that makes sense; if Firefox ever provides a way to detect an ESR version or a "normal" version of Firefox, we will update the messaging, however this is an intentional decision on behalf of the Mozilla team, so it's unlikely to change.