Deploying Firefox Proxy Settings with policies.json

For a Firefox installation you administer, put the proxy configuration in its enterprise policy rather than locating a user profile and editing generated preferences. The Proxy policy expresses the intended mode directly.

A fixed HTTP proxy used for HTTP and HTTPS destinations can be configured as follows:

{
  "policies": {
    "Proxy": {
      "Mode": "manual",
      "Locked": true,
      "HTTPProxy": "proxy.example:8080",
      "UseHTTPProxyForAllProtocols": true
    }
  }
}

Save valid UTF-8 JSON as policies.json. The hostname and port identify the proxy endpoint. This example does not configure SOCKS or provide authentication credentials.

Put the policy beside the installation

For a conventional Windows installation, create a distribution directory beside the Firefox executable and place the file there. On macOS, the corresponding location is Firefox.app/Contents/Resources/distribution. On Linux, use the installation’s distribution directory or the supported system policy location /etc/firefox/policies. Sandboxed packages can have a different policy path.

Restart Firefox, then open about:policies to examine the active policies and any errors. Confirm that the browser you restarted belongs to the installation where the file was placed. A second installation can have a different policy directory.

Choose the mode before adding endpoints

manual is appropriate for the fixed endpoint above. To follow operating-system settings, use "Mode": "system". For a known PAC URL, use "Mode": "autoConfig" with AutoConfigURL. Automatic discovery is the separate autoDetect mode.

Keep only the fields needed by the chosen mode. A PAC URL belongs in AutoConfigURL; it is not an HTTP proxy hostname. If the policy needs direct exceptions, define its Passthrough value deliberately instead of adding a broad local bypass by habit.

Locked: true makes this an enforced browser setting. Mozilla notes that existing user changes can take effect when the policy is not locked, so an unlocked default and a mandatory route have different outcomes. Choose the one the deployment actually requires.

If Windows Group Policy already manages Firefox, maintain the proxy through that established policy source. A JSON file is useful only when the browser accepts it as the relevant configuration source.