# Firefox {#sec-firefox}

## Build wrapped Firefox with extensions and policies

The `wrapFirefox` function allows to pass policies, preferences and extension that are available to firefox. With the help of `fetchFirefoxAddon` this allows build a firefox version that already comes with addons pre-installed:

```nix
{
  myFirefox = wrapFirefox firefox-unwrapped {
    nixExtensions = [
      (fetchFirefoxAddon {
        name = "ublock"; # Has to be unique!
        url = "https://addons.mozilla.org/firefox/downloads/file/3679754/ublock_origin-1.31.0-an+fx.xpi";
        sha256 = "1h768ljlh3pi23l27qp961v1hd0nbj2vasgy11bmcrlqp40zgvnr";
      })
    ];

    extraPolicies = {
      CaptivePortal = false;
      DisableFirefoxStudies = true;
      DisablePocket = true;
      DisableTelemetry = true;
      DisableFirefoxAccounts = true;
      FirefoxHome = {
        Pocket = false;
        Snippets = false;
      };
       UserMessaging = {
         ExtensionRecommendations = false;
         SkipOnboarding = true;
       };
    };

    extraPrefs = ''
      // Show more ssl cert infos
      lockPref("security.identityblock.show_extended_validation", true);
    '';
  };
}
```

If `nixExtensions != null` then all manually installed addons will be uninstalled from your browser profile.
To view available enterprise policies visit [enterprise policies](https://github.com/mozilla/policy-templates#enterprisepoliciesenabled)
or type into the Firefox url bar: `about:policies#documentation`.
Nix installed addons do not have a valid signature, which is why signature verification is disabled. This does not compromise security because downloaded addons are checksumed and manual addons can't be installed. Also make sure that the `name` field of fetchFirefoxAddon is unique. If you remove an addon from the nixExtensions array, rebuild and start Firefox the removed addon will be completly removed with all of its settings.

## Troubleshooting {#sec-firefox-troubleshooting}
If addons do not appear installed although they have been defined in your nix configuration file reset the local addon state of your Firefox profile by clicking `help -> restart with addons disabled -> restart -> refresh firefox`. This can happen if you switch from manual addon mode to nix addon mode and then back to manual mode and then again to nix addon mode.