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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    Comments are not for extended discussion; this conversation has been moved to chat.
    – MadHatter
    Nov 18, 2020 at 6:11
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    I’m voting to close this question because it shows no research effort and is based on the completely baseless idea that only stuff that's on Github can be open source. Nov 19, 2020 at 0:53
  • I disagree, I don't think that open source must be on GitHub. I've just searched the entire internet looking for the source and have found little which made me ask this question.
    – x43
    Nov 19, 2020 at 1:13
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    @x43 really? I googled on "Firefox source code", and found Mozilla's source guide as the second item on the first page of results. With respect, the ease with which one can find the source does rather make your question look like "it's not on github so is it really open-source?".
    – MadHatter
    Nov 19, 2020 at 8:22

2 Answers 2


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/


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 in the public domain doesn't make a 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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