I've been using Firefox for a while now and I am quite satisfied by it. I have always heard that it is open source, and I recently tried looking on GitHub to see if there was some sort of repo with the source in it, however, I wasn't able to find such a thing. Is the Firefox source code available to view?

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    Just because it's not on github doesn't mean it's not open source. Nov 17, 2020 at 6:18
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    – MadHatter
    Nov 18, 2020 at 6:11

3 Answers 3


Firefox is open source. It isn't hosted on GitHub, though, or even managed in Git - it's managed in mercurial and self-hosted at https://hg.mozilla.org/mozilla-central/

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    Clone it like this: hg clone https://hg.mozilla.org/mozilla-central/ firefox
    – user14263
    Dec 23, 2022 at 21:31

There is now a read-only mirror on GitHub:


which contains some helpful links to the Mercurial source, to a "How to Contribute" page, and to a page titled "Getting Set Up To Work On The Firefox Codebase".


Yes, Firefox is 100% open source. Its source code is available at https://hg.mozilla.org/mozilla-central

Adding to Mureinik's answer, here is few additional information on open source projects.

An important part for any open source project is its license.
Making a source code available doesn't make the software open source.
The author(s) has to give the permissions to the user to freely use it, modify it, and redistribute it.
This permission can be given by adding any Open Source License to the source code. It is generally a file with the name LICENSE.

Firefox is licensed under Mozilla Public License open source license. Thus it allows us to freely use it, modify it, and redistribute it, hence it 100% open source.

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