> [!NOTE]
> **Note:** You should configure your OAuth credentials using the same Google Cloud project where you have [enabled the
> Google Ads API](https://developers.google.com/google-ads/api/docs/oauth/cloud-project#enable-api) and requested an appropriate [API access level](https://developers.google.com/google-ads/api/docs/api-policy/access-levels) for the Google Ads API to work correctly.

Just like other Google APIs, Google Ads API uses the [OAuth 2.0 protocol](https://oauth.net/2/)
for authentication and authorization. OAuth 2.0 enables your Google Ads API client app
to access a user's Google Ads account without having to handle or store the user's
login info.

Broadly speaking, all the [OAuth 2.0 authorization scenarios](https://developers.google.com/identity/protocols/oauth2)
that Google supports also work with Google Ads API. However, this guide focuses on the
scenarios that are most common for Google Ads API developers.

| Scenario | Recommended approach |
|---|---|
| My app already uses one or more Google APIs. I have already built support for OAuth 2.0 workflows for my app, and just need to add Google Ads API functionality to my existing app. | 1. Make sure your authorized user or your service account has access to the Google Ads accounts you are making API calls to. For more information, see the [Google Ads access model](https://developers.google.com/google-ads/api/docs/oauth/access-model). 2. See the [multi-user authentication workflow](https://developers.google.com/google-ads/api/docs/oauth/multi-user-authentication) or the [service account workflow](https://developers.google.com/google-ads/api/docs/oauth/service-accounts) depending on the approach you are using with the rest of the Google APIs that your app is using. |
| I am building an app that manages Google Ads accounts that I already have access to. If I need to manage new Google Ads accounts in the future, I will gain access to those accounts by linking them under my Google Ads manager account. OR Someone will [invite](https://support.google.com/google-ads/answer/6372672) me to manage those accounts. | Use the [service account workflow](https://developers.google.com/google-ads/api/docs/oauth/service-accounts). If your organizational policies or account setup prevent you from using service accounts, use the [single-user authentication workflow](https://developers.google.com/google-ads/api/docs/oauth/single-user-authentication) instead. |
| I am building an app that manages Google Ads accounts on behalf of other users. My app will build a user screen that lets the signed-in users connect to their Google Ads accounts and authorize my app to manage those accounts on their behalf. | Use [multi-user authentication](https://developers.google.com/google-ads/api/docs/oauth/multi-user-authentication). |

To review and revoke access for third-party applications connected to your
Google Account, visit your [Google Account permissions page](https://myaccount.google.com/permissions).