Browsers × operating systems
All Chromium-based and Gecko-based targets work on Windows, macOS, and Linux. Safari is the exception: running it needs macOS with full Xcode.extension build --browser=safari still produces the complete dist/safari bundle on Windows and Linux, skipping the Xcode packaging step with a warning.
See Browsers available for target names and flags, and Building Safari extensions for the Safari workflow and limitations.
Frameworks × dev update model
Every framework gets automatic detection, bundling, and dev-time updates. What differs is the update model: whether an edit hot-swaps code in place or reloads the surface. See Reload and HMR for the underlying tiers.CSS tooling × what installs automatically
Plain CSS and CSS Modules are built in. Preprocessors need their toolchain installed in your project: when it is missing, Extension.js warns, names the file, and ships the source uncompiled rather than installing anything for you. Tailwind rides through the PostCSS pipeline and is installed by you.Package managers
npm, pnpm, yarn, bun, and deno are all supported for create, dev, and build. Deno projects scaffold a deno.jsonc instead of a package.json; the toolchain is manifest-agnostic. See Create your first extension for the Deno-specific notes.