CODEFOSSIL · fossil records
What does a codebase remember?
Every function has a history: when it was born, what changed it, what broke it, who depends on it. These pages were built from three well-known repositories' own Git history, with every claim labelled as observed, computed or inferred.
expressjs/express
6,177 commits · 396 authors · since 2009
res.get has not changed a character since 2011. res.send has been fixed 17 times, most recently in 2026.
facebook/react
21,712 commits · since the first public release in 2013
isEventSupported shipped in the initial public release and is still there, 13 years later.
pallets/flask
5,562 commits · 858 authors · since 2010
render_template has moved house three times since the first commit, and is followed back through every move.
Make one for your repository
cd your-repository npx codefossil site fossil-site
Or ask about one function: npx codefossil why parseConfig. Everything runs on your machine; no account, no upload, no AI needed.
How sure is it?
- FACT: read directly from Git (this commit exists, this function is defined here).
- DERIVED: computed from facts (this commit introduced it; it changed 78 times).
- INFERRED: a heuristic reading (this commit looks like a fix; this workaround may be obsolete).