The client-side of the Chrome DevTools, including all JS & CSS to run the DevTools webapp.
The version number of the npm package (e.g.
1.0.373466) refers to the Chromium commit position of latest frontend git commit. It's incremented with every Chromium commit, however the package is updated roughly daily.
The frontend is available through a git subtree mirror on chromium.googlesource.com, with a regularly updating GitHub mirror at github.com/ChromeDevTools/devtools-frontend. The codebase's true location is in
third_party/WebKit/Source/devtools/ in Chromium's git repo.