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Configuring Firefox for Tor on Linux

Caution

This guide assumes you have completed setting up Tor. Please visit this section first before you proceed as it is required for Firefox to properly work with Tor.

  1. Open Firefox and enter about:config in the URL bar. Accept any warnings that may appear about accessing advanced settings.

  2. Search for dom.securecontext.allowlist_onions and set the value to true.

    Firefox whitelist onions screenshot
  3. Download a Proxy Auto Config file to inform Firefox how to use the Tor daemon running on your computer. You can get Start9’s standard file from a terminal, by using:

    sudo wget -P /etc/tor https://registry.start9labs.com/sys/proxy.pac
    
  4. Now, back in your Firefox web browser, select Settings from the right-hand hamburger menu:

    Firefox options screenshot
  5. Search for the term “proxy” in the search bar in the upper right, then select the button that says Settings…:

    Firefox search screenshot
  6. This should open a menu that will allow you to configure your proxy settings. Select Automatic proxy configuration URL and paste in the path to your PAC file from earlier, prefixed with file://. For example:

    file:///etc/tor/proxy.pac
    
  7. Then, check the box labeled Proxy DNS when using SOCKS v5:

    Firefox proxy settings screenshot
  8. Click OK and then restart Firefox for the changes to take effect.

  9. You’re all set! You should now be able to navigate to .onion URLs in Firefox. This means you can access tor-only service WebUIs, such as Cups Messenger, and use your Vaultwarden Tor address in the Bitwarden Firefox Plugin. You can test this by going to Start9’s .onion homepage, here.