# Monitor App Check request metrics

After you add the App Check library to your app, but before you enable
App Check enforcement, you should make sure that doing so won't disrupt your
existing legitimate users.

An important tool you can use to make this decision are App Check
request metrics. You can monitor App Check metrics in the
[Google API Console](https://developers.google.com/identity/sign-in/ios/appcheck/monitor-metrics#monitor_metrics_in_the_google_cloud_console) or the [Firebase Console](https://developers.google.com/identity/sign-in/ios/appcheck/monitor-metrics#monitor_metrics_in_the_firebase_console).

## Monitor Metrics in the Google API Console

To view metrics for your iOS OAuth client, navigate to the edit view of the
client in the [Credentials page](https://console.cloud.google.com/apis/credentials). There, you will see metrics to the
right of the page under the **Google Identity for iOS** section. These metrics
will show you your App Check request metrics. The metrics include the
following information:

- **Number of verified requests** - requests that have a valid App Check token. After you enable App Check enforcement, only requests in this category will succeed.
- **Number of unverified requests: likely outdated client requests** - requests missing an App Check token; these request may be from an older version of your app that doesn't include an App Check implementation.
- **Number of unverified requests: unknown origin requests** - requests missing an App Check token that don't look like they are coming from your app.
- **Number of unverified requests: invalid requests** - requests with an invalid App Check token, which may be from an inauthentic client attempting to impersonate your app, or from emulated environments.

## Monitor Metrics in the Firebase Console

You can view metrics for your projects as a whole, or
for individual OAuth clients:

- To view the App Check request metrics for your project, open the
  [App Check](https://console.firebase.google.com/project/_/appcheck) section of the Firebase console and expand the
  **Google Identity for iOS** section. For example:

  ![Screenshot of the App Check metrics page](https://developers.google.com/static/identity/sign-in/ios/appcheck/app-check-metrics.png)
- To view the App Check request metrics for a specific OAuth client, open the
  [OAuth clients](https://console.firebase.google.com/project/_/appcheck/products/oauth) page of the Firebase console and
  expand the section corresponding to the client.

The request metrics are broken down into four categories:

- **Verified** requests are those that have a valid App Check token. After
  you enable App Check enforcement, only requests in this category will
  succeed.

- **Outdated client** requests are those that are missing an App Check
  token. These requests might be from an older version of the Firebase SDK
  before App Check was included in the app.

- **Unknown origin** requests are those that are missing an App Check token,
  and don't look like they come from the Firebase SDK. These might be from
  requests made with stolen API keys or forged requests made without the
  Firebase SDK.

- **Invalid** requests are those that have an invalid
  App Check token, which might be from an inauthentic client attempting to
  impersonate your app, or from emulated environments.

The distribution of these categories for your app should inform when you decide
to enable enforcement. Here are some guidelines:

- If almost all of the recent requests are from verified clients, consider
  enabling enforcement to start protecting your auth endpoints.

- If a significant portion of the recent requests are from likely-outdated
  clients, to avoid disrupting users, consider waiting for more users to update
  your app before enabling enforcement. Enforcing App Check on a released
  app will break prior app versions that are not integrated with the
  App Check SDK.

- If your app hasn't launched yet, you should enable App Check enforcement
  immediately, since there aren't any outdated clients in use.

## Next steps

When you understand how App Check will affect your users and you're ready to
proceed, you can [enable App Check enforcement](https://developers.google.com/identity/sign-in/ios/appcheck/enable-enforcement).