Source code for all Mozilla projects hosted in the Mercurial and CVS repositories can be searched and viewed online using MXR. It's an enhanced and improved variant of the original Linux Cross Reference tool.
A newer searchable cross-reference named DXR is also available - it does not offer all the roots that MXR does, but its results can be more complete.
Some other MXR roots of interest are:
- "mozilla-central" contains current Firefox and Gecko development. Releases branch off of this repository. Also known as "Trunk" .
- "comm-central" contains current Thunderbird, SeaMonkey and Calendar development. Also contains a mirror of mozilla-central. Releases branch off of this repository.
- "mozilla-1.9.1" contains Branch development on Firefox 3.5 and Gecko 1.9.1.
- "comm-1.9.1" contains Branch development for Thunderbird 3, SeaMonkey 2 and Sunbird 1 with Gecko 1.9.1. Also contains a mirror of mozilla-1.9.1.
- "mozilla" root contains the 1.9 branch code, like "seamonkey", but indexes a bigger part of the repository and is updated less often.
- Mozilla 1.8 root contains Firefox, Thunderbird 2.0.0.x, and SeaMonkey 1.1.x
- Mozilla 1.8.0 root contains Firefox, Thunderbird 1.5.0.x, SeaMonkey 1.0.x
- Aviary 1.0.1 root Firefox and Thunderbird 1.0.0.x
- Mozilla 1.7 root contains Mozilla Suite 1.7.x
Mozilla Source Code Directory Structure has a short description of the code living in each source directory of the tree.
To view the source code of a specific version, you can also download it. Each product produced by Mozilla is archived there, together with its source code.