vulpine

A compact Firefox theme in plain userChrome.css. Navigation buttons, the URL bar and every tab share a single row. No fork, no build, no extension.

Install

npx vulpine

The same command on Windows, macOS and Linux. Quit Firefox first, then start it again once the installer is done. Node 16.7+ is the only requirement.

It targets the profile your browser actually opens, backs up any chrome/ folder already sitting there instead of overwriting it, and appends its prefs to user.js without disturbing what you already keep in that file. Firefox, LibreWolf, Waterfox, Floorp, Zen and Mullvad are all detected — on Linux, Flatpak and Snap installs included.

Flag
--all	install into every profile found, no question asked
--profile <path>	target one specific profile
--uninstall	remove the theme and the prefs it set
--force	don't stop when the browser is still running
--link	symlink chrome/ instead of copying it, from a clone

Make it yours

Every knob lives in chrome/modules/_variables.css:

Variable
--vp-row-height	height of the row
--vp-gap	horizontal spacing between every item in the row
--vp-urlbar-width	fixed width of the URL bar
--vp-tab-height, --vp-tab-radius	tab shape
--vp-bg-toolbar, --vp-bg-field, --vp-bg-tab-selected	the three colours that carry the theme
--vp-color-scheme	dark or light — keep it in sync with your palette

Hit Ctrl+Shift+R in the Browser Toolbox to reload the chrome without restarting.

Uninstall

npx vulpine --uninstall

The theme is removed, the prefs block is stripped out of user.js while the rest of the file stays, and any backup taken at install time is reported back to you.

Notes

Built and tested against Firefox Nightly 157 on Windows 11. Chrome selectors and theme tokens move between major releases, so expect to patch things after an update. docs/internals.md covers how the single row is built, where to find the real selectors, and the traps worth knowing about.

MIT.