I am aware that Firefox has nightly builds available at https://nightly.mozilla.org/ and was wondering what the difference was between the stable and nightly builds. Are they safe to use or are they primarily for beta testing?

  • Nightly builds are pretty much state builds and are not stable releases. They are more or less testing releases that are just made available to the public. For the most part, they'll work, but they should not be used as a regular production version.
    – MaQleod
    Aug 31, 2011 at 20:35

3 Answers 3


Nightly builds feature the absolute latest changes, and are considered unstable. They are the most buggy, and will result in a higher crash count than stable Firefox Releases. They are to be used for seeking bugs, and then submitting them to Mozilla developers, so that the Beta and Release channels do not suffer from such bugs.

Nightly is usually many versions ahead - Currently on 9. So you will be seeing features added long before others, but at the risk of crashing more, and potentially broken parts of Firefox. I can confirm this by using x64 Nightly and not being able to use Flash properly anymore (Crashes x64 Flash)

They are to be used at your own risk and discretion. As they say, "These builds are for testing purposes only.", so don't count on Nightly when working.

  • Thanks. Is it possible to run both the nightly builds and stable releases at the same time? Aug 31, 2011 at 20:58
  • You can. They are stored in separate locations. I use both personally. Aug 31, 2011 at 21:01
  • And before you ask (if you were planning to) you should make a new question along the lines of "How do I install production Firefox and Nightly Release Firefox on the same machine"
    – EBGreen
    Aug 31, 2011 at 21:07
  • @EBGreen You download both installers, install both. It doesn't require anything fancy. Aug 31, 2011 at 21:08
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    @EBGreen It does not need to be another question though. Aug 31, 2011 at 21:11

The very top of the nightly build page:

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  • 1
    ...and the developers' page: Nightly Builds: the Bleeding Edge Created most weekdays from the previous day's work, these builds may or may not work. Use them to verify that a bug you're tracking has been fixed. We make nightly builds for testing only. We write code and post the results right away so people like you can join our testing process and report bugs. You will find bugs, and lots of them. Mozilla might crash on startup. It might delete all your files and cause your computer to burst into flames. Don't bother downloading nightly builds if you're unwilling to put up with problems.
    – Linker3000
    Aug 31, 2011 at 20:46
  • @Linker3000/EBGreen - Thanks. Please see my follow-up question to Simon Aug 31, 2011 at 20:59

They're for those who want to live on the bleeding edge and don't mind instability as part if their daily browsing life. Maybe they're developers or testers.

People who want mostly stable builds should use Firefox's Beta Channel. If you want to be in on the newest features with the occasional crash, there's the Aurora Channel.

You can choose from the channels at http://www.mozilla.org/en-US/firefox/channel/


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