Locking a Firefox PAC URL with Enterprise Policy

Publish a managed PAC URL with Firefox’s Proxy policy, lock it when required, and check policy acceptance separately from script retrieval.

A managed Firefox installation can receive a PAC URL through Mozilla’s Proxy enterprise policy. Lock the policy when users should not replace that routing configuration.

The Proxy policy can choose manual settings, a PAC URL, system settings, or other documented modes. It also has a lock option, which matters when users report that their local proxy changes do not stick.

A managed PAC configuration

The equivalent policy data can be represented as:

{
  "policies": {
    "Proxy": {
      "Mode": "autoConfig",
      "AutoConfigURL": "https://config.example/proxy.pac",
      "Locked": true
    }
  }
}

These are the policy keys to distribute. Distribute the configuration through the management mechanism appropriate to the installation. Replace the example URL with the organization's approved script endpoint.

Use the Proxy policy reference for the accepted values and the policy configuration guide for deployment. Keep the available policy templates and the Firefox version in view; an unsupported key should not be treated as applied simply because the file is valid JSON.

Inspect what Firefox accepted

Check about:policies for the effective policy and reported errors. Then establish whether the PAC was retrieved and which route it selects for the affected destination. These are separate checks: accepting a policy does not establish that the configuration URL is reachable.

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