Install command

    Use install to add a managed browser runtime into the Extension.js cache.

    This is most useful when you want a deterministic browser binary for dev, build, start, or preview, especially for Chrome for Testing, Chromium, Firefox, or Edge.

    Canonical usage

    For a single browser, use the positional form:

    npm
    pnpm
    yarn
    extension install <browser>

    Use --browser only when you need multiple targets, browser families, or all.

    What install does

    CapabilityWhat it gives you
    Managed browser cacheStable install location under the Extension.js browser cache
    Deterministic runtimeConsistent binaries for repeatable local runs and automation
    Cross-browser setupOne command flow for Chrome, Chromium, Edge, and Firefox
    Path discovery--where reveals the resolved cache root or browser-specific install path

    Usage

    npm
    pnpm
    yarn
    extension install [browser-name] [options]

    Arguments and flags

    Flag / argumentWhat it doesDefault
    [browser-name]Install a single browser target such as chrome, chromium, edge, or firefoxchromium
    --browser <chrome|chromium|edge|firefox|chromium-based|gecko-based|firefox-based|all>Override the positional browser name and support multi-target installsunset
    --wherePrint the resolved managed cache root, or browser-specific install pathdisabled

    Examples

    Install Chrome for Testing

    extension install chrome

    Install multiple targets in one command

    extension install --browser chrome,firefox

    Show the managed install path for Chrome

    extension install chrome --where

    Cache locations

    By default, Extension.js stores managed browsers in a stable per-user cache:

    • macOS: ~/Library/Caches/extension.js/browsers
    • Linux: ~/.cache/extension.js/browsers or $XDG_CACHE_HOME/extension.js/browsers
    • Windows: %LOCALAPPDATA%\extension.js\browsers

    You can override the cache root with EXT_BROWSERS_CACHE_DIR.

    Notes

    • chrome installs Chrome for Testing rather than relying on the system Google Chrome app.
    • edge may require a privileged interactive session on Linux.
    • install only manages browsers inside the Extension.js cache. It does not modify system browser installs.