Mastering Chromium: How to Launch with Command-Line Switches for Enhanced Control

Chromium, the open-source project behind Google Chrome, offers a plethora of command-line switches that allow you to fine-tune its behavior. These switches can enable experimental features, modify default functionalities, and aid in debugging. This guide provides a comprehensive overview of how to use these switches across various operating systems.

While a complete list doesn't exist, a substantial collection can be found at Peter Beverloo's Chromium Command Line Switches.

Important Considerations:

• Switches vs. Flags: Be aware that Chrome switches (e.g., --incognito) are distinct from Chrome flags (e.g., chrome://flags/#ignore-gpu-blocklist). A feature might be enabled through either a switch, a flag, or both.
• Purpose: Some switches are for development and may be unstable or removed without notice. For managing Chrome in enterprise environments, use Chrome Enterprise Policies instead.
• Verification: Don't solely rely on chrome://flags to confirm if a switch is active. The most reliable method is to check chrome://version for the complete command line used by the current instance.

How to Implement Command-Line Switches on Different Platforms

Windows

1. Close Chromium: Ensure all Chrome instances are closed by navigating to chrome://quit.
2. Shortcut Properties: Right-click your Chrome shortcut and select "Properties."
3. Modify Target: In the "Target:" field, add the desired switch at the end of the existing path. For instance: "C:\Program Files\Google\Chrome\Application\chrome.exe" --disable-gpu-vsync
4. Launch: Start Chrome using the modified shortcut.

macOS

1. Quit Chromium: Fully quit Chromium using chrome://quit.

2. Open Terminal: Launch your preferred terminal application.

3. Execute Command: Run Chromium with the desired switch. Remember to escape spaces in the path for Google Chrome:

   /Applications/Chromium.app/Contents/MacOS/Chromium --remote-debugging-port=9222
   # For Google Chrome:
   /Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome --remote-debugging-port=9222
   

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Linux

1. Close Chromium: Exit all running instances of Chromium.

2. Open Terminal: Open your terminal emulator.

3. Run Command: Start Chromium with the switch. Use chromium-browser or google-chrome depending on which browser you're using:

   chromium-browser --remote-debugging-port=9222
   google-chrome --foo --bar=2
   

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iOS

• Custom Builds: Only Chromium builds compiled from source code support command-line switches on iOS.
  1. Open the Settings app
  2. Go to Chromium/Experimental Settings
  3. Add your switches in the "Extra flags (one per line)". Switch on the "Append Extra Flags" setting.
• Official Releases: Google Chrome from the App Store or TestFlight does not support command-line switches.

Harnessing V8 Flags

The V8 JavaScript engine (powering Chromium and Chrome) can be configured via Chrome's js-flags switch.

• Example: To trace V8 optimizations:

  chrome.exe --js-flags="--trace-opt --trace-deopt --trace-bailout"
  

• Listing Flags: Obtain a complete list of V8 flags using:

  chrome.exe --js-flags="--help"
  

• V8 Documentation: Explore additional flags in the V8 documentation.

Android

Access about:version within the app to see the active command-line switches.

Rooted Devices/Debug Builds:

out/Default/bin/chrome_public_apk argv # Show existing switches
out/Default/bin/content_shell_apk argv --args='--foo --bar' # Set new switches

Install and Run with Switches:

out/Default/bin/chrome_public_apk run --args='--foo --bar'
out/Default/bin/content_shell_apk run # Clears any existing switches

Production Builds (Non-Rooted):

1. Enable "Enable command line on non-rooted devices" in chrome://flags.
2. Set command-line arguments in /data/local/tmp/chrome-command-line. The first argument must be an underscore ("_").
3. Manually restart Chrome (the "Relaunch" button in chrome://flags may not be sufficient). See crbug.com/784947 for further information.

ContentShell on Android

ContentShell provides an alternative way to set switches:

1. Download an LKGR (Last Known Good Revision) build.

2. Install ContentShell.apk from the downloaded archive.

3. Use the following command:

   adb shell am start \
    -a android.intent.action.VIEW \
    -n org.chromium.content_shell_apk/.ContentShellActivity \
    --es activeUrl "http://chromium.org" \
    --esa commandLineArgs --show-paint-rects,--show-property-changed-rects
   

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Android WebView

Refer to the Chromium tree documentation for WebView-specific command-line flags.

Chrome OS

1. Enter dev mode, disable rootfs verification, and access a command prompt (see Chromium OS Developer Mode documentation).
2. Modify /etc/chrome_dev.conf. Consult the file's comments for instructions.
3. Restart the UI: sudo restart ui

By following these steps, you can leverage Chromium's command-line switches to customize your browsing experience, test new features, and troubleshoot issues. Remember to use these powerful tools responsibly and be aware of their potential impact on stability.