OAuth 2.0 for Mobile & Desktop Apps

Note: If you are new to OAuth 2.0, we recommend that you read the OAuth 2.0 overview before getting started. The overview summarizes OAuth 2.0 flows that Google supports, which can help you to ensure that you've selected the right flow for your application.

This document explains how applications installed on devices like phones, tablets, and computers use Google's OAuth 2.0 endpoints to authorize access to Google APIs.

OAuth 2.0 allows users to share specific data with an application while keeping their usernames, passwords, and other information private. For example, an application can use OAuth 2.0 to obtain permission from users to store files in their Google Drives.

Installed apps are distributed to individual devices, and it is assumed that these apps cannot keep secrets. They can access Google APIs while the user is present at the app or when the app is running in the background.

This authorization flow is similar to the one used for web server applications. The main difference is that installed apps must open the system browser and supply a local redirect URI to handle responses from Google's authorization server.

Alternatives

For mobile apps, you may prefer to use Google Sign-in for Android or iOS. The Google Sign-in client libraries handle authentication and user authorization, and they may be simpler to implement than the lower-level protocol described here.

For apps running on devices that do not support a system browser or that have limited input capabilities, such as TVs, game consoles, cameras, or printers, see OAuth 2.0 for TVs & Devices or Sign-In on TVs and Limited Input Devices.

Libraries and samples

We recommend the following libraries and samples to help you implement the OAuth 2.0 flow described in this document:

• AppAuth for Android library
• AppAuth for iOS library
• OAuth for Apps: Windows Samples

Prerequisites

Enable APIs for your project

Any application that calls Google APIs needs to enable those APIs in the API Console.

To enable an API for your project:

1. Open the API Library in the Google API Console.
2. If prompted, select a project, or create a new one.
3. The API Library lists all available APIs, grouped by product family and popularity. If the API you want to enable isn't visible in the list, use search to find it, or click View All in the product family it belongs to.
4. Select the API you want to enable, then click the Enable button.
5. If prompted, enable billing.
6. If prompted, read and accept the API's Terms of Service.

Create authorization credentials

Any application that uses OAuth 2.0 to access Google APIs must have authorization credentials that identify the application to Google's OAuth 2.0 server. The following steps explain how to create credentials for your project. Your applications can then use the credentials to access APIs that you have enabled for that project.

1. Go to the Credentials page.
2. Click Create credentials > OAuth client ID.
3. The following sections describe the client types that Google's authorization server supports. Choose the client type that is recommended for your application, name your OAuth client, and set the other fields in the form as appropriate.

Android

1. Select the Android application type.
2. Enter a name for the OAuth client. This name is displayed on your project's Credentials page to identify the client.
3. Enter the package name of your Android app. This value is defined in the package attribute of the <manifest> element in your app manifest file.
4. Enter the SHA-1 signing certificate fingerprint of the app distribution.
   • If your app uses app signing by Google Play, copy the SHA-1 fingerprint from the app signing page of the Play Console.
   • If you manage your own keystore and signing keys, use the keytool utility included with Java to print certificate information in a human-readable format. Copy the SHA1 value in the Certificate fingerprints section of the keytool output. See Authenticating Your Client in the Google APIs for Android documentation for more information.
5. (Optional) Verify ownership of your Android application.
6. Click Create.

iOS

1. Select the iOS application type.
2. Enter a name for the OAuth client. This name is displayed on your project's Credentials page to identify the client.
3. Enter the bundle identifier for your app. The bundle ID is the value of the CFBundleIdentifier key in your app's information property list resource file (info.plist). The value is most commonly displayed in the General pane or the Signing & Capabilities pane of the Xcode project editor. The bundle ID is also displayed in the General Information section of the App Information page for the app on Apple's App Store Connect site.

   Confirm that you are using the correct bundle ID for your app, as you won't be able to change it if you are using the App Check feature.

4. (Optional)

   Enter your app's App Store ID if the app is published in Apple's App Store. The Store ID is a numeric string included in every Apple App Store URL.

   1. Open the Apple App Store app on your iOS or iPadOS device.
   2. Search for your app.
   3. Select the Share button (square and arrow up symbol).
   4. Select Copy Link.
   5. Paste the link into a text editor. The App Store ID is the final part of the URL.

      Example: https://apps.apple.com/app/google/id284815942

5. (Optional)

   Enter your Team ID. See Locate your Team ID in the Apple Developer Account documentation for more information.

   Note: The Team ID field is required if you are enabling App Check for your client.
6. (Optional)

   Enable App Check for your iOS app. When you enable App Check, Apple's App Attest service is used to verify that OAuth 2.0 requests originating from your OAuth client are genuine and come from your app. This helps to reduce the risk of app impersonation. Learn more about enabling App Check for your iOS app.

7. Click Create.

UWP

1. Select the Universal Windows Platform application type.
2. Enter a name for the OAuth client. This name is displayed on your project's Credentials page to identify the client.
3. Enter your app's 12-character Microsoft Store ID. You can find this value in Microsoft Partner Center on the App identity page in the App management section.
4. Click Create.

For UWP apps, the custom URI scheme cannot be longer than 39 characters.

Identify access scopes

Scopes enable your application to only request access to the resources that it needs while also enabling users to control the amount of access that they grant to your application. Thus, there may be an inverse relationship between the number of scopes requested and the likelihood of obtaining user consent.

Before you start implementing OAuth 2.0 authorization, we recommend that you identify the scopes that your app will need permission to access.

Note: Incremental authorization is not supported for installed apps or devices.

The OAuth 2.0 API Scopes document contains a full list of scopes that you might use to access Google APIs.

If your public application uses scopes that permit access to certain user data, it must complete a verification process. If you see unverified app on the screen when testing your application, you must submit a verification request to remove it. Find out more about unverified apps and get answers to frequently asked questions about app verification in the Help Center.

Obtaining OAuth 2.0 access tokens

The following steps show how your application interacts with Google's OAuth 2.0 server to obtain a user's consent to perform an API request on the user's behalf. Your application must have that consent before it can execute a Google API request that requires user authorization.

Step 1: Generate a code verifier and challenge

Google supports the Proof Key for Code Exchange (PKCE) protocol to make the installed app flow more secure. A unique code verifier is created for every authorization request, and its transformed value, called "code_challenge", is sent to the authorization server to obtain the authorization code.

Create the code verifier

A code_verifier is a high-entropy cryptographic random string using the unreserved characters [A-Z] / [a-z] / [0-9] / "-" / "." / "_" / "~", with a minimum length of 43 characters and a maximum length of 128 characters.

The code verifier should have enough entropy to make it impractical to guess the value.

Create the code challenge

Two methods of creating the code challenge are supported.

Code Challenge Generation Methods
S256 (recommended)	The code challenge is the Base64URL (with no padding) encoded SHA256 hash of the code verifier. code_challenge = BASE64URL-ENCODE(SHA256(ASCII(code_verifier)))
plain	The code challenge is the same value as the code verifier generated above. code_challenge = code_verifier

Step 2: Send a request to Google's OAuth 2.0 server

To obtain user authorization, send a request to Google's authorization server at https://accounts.google.com/o/oauth2/v2/auth. This endpoint handles active session lookup, authenticates the user, and obtains user consent. The endpoint is only accessible over SSL, and it refuses HTTP (non-SSL) connections.

The authorization server supports the following query string parameters for installed applications:

Parameters
client_id	Required The client ID for your application. You can find this value in the API Console Credentials page.
redirect_uri	Required Determines how Google's authorization server sends a response to your app. There are several redirect options available to installed apps, and you will have set up your authorization credentials with a particular redirect method in mind. The value must exactly match one of the authorized redirect URIs for the OAuth 2.0 client, which you configured in your client's API Console Credentials page. If this value doesn't match an authorized URI, you will get a redirect_uri_mismatch error. The table below shows the appropriate redirect_uri parameter value for each method: redirect_uri values Custom URI scheme com.example.app:redirect_uri_path or com.googleusercontent.apps.123:redirect_uri_path com.example.app is the reverse DNS notation of a domain under your control. The custom scheme must contain a period to be valid. com.googleusercontent.apps.123 is the reverse DNS notation of the client ID. redirect_uri_path is an optional path component, such as /oauth2redirect. Note that the path should begin with a single slash, which is different from regular HTTP URLs. Note : Custom URI schemes are no longer supported on Chrome apps and are disabled by default on Android. Learn more about custom scheme alternatives for Android and Chrome apps. Loopback IP address http://127.0.0.1:port or http://[::1]:port Query your platform for the relevant loopback IP address and start an HTTP listener on a random available port. Substitute port with the actual port number your app listens on. Note that support for the loopback IP address redirect option on mobile apps is DEPRECATED.
response_type	Required Determines whether the Google OAuth 2.0 endpoint returns an authorization code. Set the parameter value to code for installed applications.
scope	Required A space-delimited list of scopes that identify the resources that your application could access on the user's behalf. These values inform the consent screen that Google displays to the user. Scopes enable your application to only request access to the resources that it needs while also enabling users to control the amount of access that they grant to your application. Thus, there is an inverse relationship between the number of scopes requested and the likelihood of obtaining user consent.
code_challenge	Recommended Specifies an encoded code_verifier that will be used as a server-side challenge during authorization code exchange. See create code challenge section above for more information.
code_challenge_method	Recommended Specifies what method was used to encode a code_verifier that will be used during authorization code exchange. This parameter must be used with the code_challenge parameter described above. The value of the code_challenge_method defaults to plain if not present in the request that includes a code_challenge. The only supported values for this parameter are S256 or plain.
state	Recommended Specifies any string value that your application uses to maintain state between your authorization request and the authorization server's response. The server returns the exact value that you send as a name=value pair in the URL fragment identifier (#) of the redirect_uri after the user consents to or denies your application's access request. You can use this parameter for several purposes, such as directing the user to the correct resource in your application, sending nonces, and mitigating cross-site request forgery. Since your redirect_uri can be guessed, using a state value can increase your assurance that an incoming connection is the result of an authentication request. If you generate a random string or encode the hash of a cookie or another value that captures the client's state, you can validate the response to additionally ensure that the request and response originated in the same browser, providing protection against attacks such as cross-site request forgery. See the OpenID Connect documentation for an example of how to create and confirm a state token. Important: The OAuth client must prevent CSRF as called out in the OAuth2 Specification . One way to achieve this is by using the state parameter to maintain state between your authorization request and the authorization server's response.
login_hint	Optional If your application knows which user is trying to authenticate, it can use this parameter to provide a hint to the Google Authentication Server. The server uses the hint to simplify the login flow either by prefilling the email field in the sign-in form or by selecting the appropriate multi-login session. Set the parameter value to an email address or sub identifier, which is equivalent to the user's Google ID.

Note: incremental authorization with installed apps is not supported due to the fact that the client cannot keep the client_secret confidential.

Sample authorization URLs

The tabs below show sample authorization URLs for the different redirect URI options.

The URLs are identical except for the value of the redirect_uri parameter. The URLs also contain the required response_type and client_id parameters as well as the optional state parameter. Each URL contains line breaks and spaces for readability.

Custom URI scheme

https://accounts.google.com/o/oauth2/v2/auth?
 scope=email%20profile&
 response_type=code&
 state=security_token%3D138r5719ru3e1%26url%3Dhttps%3A%2F%2Foauth2.example.com%2Ftoken&
 redirect_uri=com.example.app%3A/oauth2redirect&
 client_id=client_id

Loopback IP address

https://accounts.google.com/o/oauth2/v2/auth?
 scope=email%20profile&
 response_type=code&
 state=security_token%3D138r5719ru3e1%26url%3Dhttps%3A%2F%2Foauth2.example.com%2Ftoken&
 redirect_uri=http%3A//127.0.0.1%3A9004&
 client_id=client_id

Step 3: Google prompts user for consent

In this step, the user decides whether to grant your application the requested access. At this stage, Google displays a consent window that shows the name of your application and the Google API services that it is requesting permission to access with the user's authorization credentials and a summary of the scopes of access to be granted. The user can then consent to grant access to one or more scopes requested by your application or refuse the request.

Your application doesn't need to do anything at this stage as it waits for the response from Google's OAuth 2.0 server indicating whether any access was granted. That response is explained in the following step.

Errors

Requests to Google's OAuth 2.0 authorization endpoint may display user-facing error messages instead of the expected authentication and authorization flows. Common error codes and suggested resolutions are listed below.

admin_policy_enforced

The Google Account is unable to authorize one or more scopes requested due to the policies of their Google Workspace administrator. See the Google Workspace Admin help article Control which third-party & internal apps access Google Workspace data for more information about how an administrator may restrict access to all scopes or sensitive and restricted scopes until access is explicitly granted to your OAuth client ID.

disallowed_useragent

The authorization endpoint is displayed inside an embedded user-agent disallowed by Google's OAuth 2.0 Policies.

Android

Android developers may encounter this error message when opening authorization requests in android.webkit.WebView. Developers should instead use Android libraries such as Google Sign-In for Android or OpenID Foundation's AppAuth for Android.

Web developers may encounter this error when an Android app opens a general web link in an embedded user-agent and a user navigates to Google's OAuth 2.0 authorization endpoint from your site. Developers should allow general links to open in the default link handler of the operating system, which includes both Android App Links handlers or the default browser app. The Android Custom Tabs library is also a supported option.

iOS

iOS and macOS developers may encounter this error when opening authorization requests in WKWebView. Developers should instead use iOS libraries such as Google Sign-In for iOS or OpenID Foundation's AppAuth for iOS.

Web developers may encounter this error when an iOS or macOS app opens a general web link in an embedded user-agent and a user navigates to Google's OAuth 2.0 authorization endpoint from your site. Developers should allow general links to open in the default link handler of the operating system, which includes both Universal Links handlers or the default browser app. The SFSafariViewController library is also a supported option.

org_internal

The OAuth client ID in the request is part of a project limiting access to Google Accounts in a specific Google Cloud Organization. For more information about this configuration option see the User type section in the Setting up your OAuth consent screen help article.

invalid_grant

If you are using a code verifier and challenge, the code_callenge parameter is invalid or missing. Ensure that the code_challenge parameter is set correctly.

When refreshing an access token, the token may have expired or has beeninvalidated. Authenticate the user again and ask for user consent to obtain new tokens. If you are continuing to see this error, ensure that your application has been configured correctly and that you are using the correct tokens and parameters in your request. Otherwise, the user account may have been deleted or disabled.

redirect_uri_mismatch

The redirect_uri passed in the authorization request does not match an authorized redirect URI for the OAuth client ID. Review authorized redirect URIs in the Google API Console Credentials page.

The passed redirect_uri may be invalid for the client type.

The redirect_uri parameter may refer to the OAuth out-of-band (OOB) flow that has been deprecated and is no longer supported. Refer to the migration guide to update your integration.

invalid_request

There was something wrong with the request you made. This could be due to a number of reasons:

• The request was not properly formatted
• The request was missing required parameters
• The request uses an authorization method that Google doesn't support. Verify your OAuth integration uses a recommended integration method
• A custom scheme is used for the redirect uri : If you see the error message Custom URI scheme is not supported on Chrome apps or Custom URI scheme is not enabled for your Android client, it means you are using a custom URI scheme which isn't supported on Chrome apps and is disabled by default on Android. Learn more about custom URI scheme alternatives

Step 4: Handle the OAuth 2.0 server response

The manner in which your application receives the authorization response depends on the redirect URI scheme that it uses. Regardless of the scheme, the response will either contain an authorization code (code) or an error (error). For example, error=access_denied indicates that the user declined the request.

If the user grants access to your application, you can exchange the authorization code for an access token and a refresh token as described in the next step.

Step 5: Exchange authorization code for refresh and access tokens

To exchange an authorization code for an access token, call the https://oauth2.googleapis.com/token endpoint and set the following parameters:

Fields
client_id	The client ID obtained from the API Console Credentials page.
client_secret	The client secret obtained from the API Console Credentials page.
code	The authorization code returned from the initial request.
code_verifier	The code verifier you created in Step 1.
grant_type	As defined in the OAuth 2.0 specification, this field's value must be set to authorization_code.
redirect_uri	One of the redirect URIs listed for your project in the API Console Credentials page for the given client_id.

The following snippet shows a sample request:

POST /token HTTP/1.1
Host: oauth2.googleapis.com
Content-Type: application/x-www-form-urlencoded

code=4/P7q7W91a-oMsCeLvIaQm6bTrgtp7&
client_id=your_client_id&
client_secret=your_client_secret&
redirect_uri=http://127.0.0.1:9004&
grant_type=authorization_code

Google responds to this request by returning a JSON object that contains a short-lived access token and a refresh token.

The response contains the following fields:

Fields
access_token	The token that your application sends to authorize a Google API request.
expires_in	The remaining lifetime of the access token in seconds.
id_token	Note: This property is only returned if your request included an identity scope, such as openid, profile, or email. The value is a JSON Web Token (JWT) that contains digitally signed identity information about the user.
refresh_token	A token that you can use to obtain a new access token. Refresh tokens are valid until the user revokes access. Note that refresh tokens are always returned for installed applications.
scope	The scopes of access granted by the access_token expressed as a list of space-delimited, case-sensitive strings.
token_type	The type of token returned. At this time, this field's value is always set to Bearer.

Important: Your application should store both tokens in a secure, long-lived location that is accessible between different invocations of your application. The refresh token enables your application to obtain a new access token if the one that you have expires. As such, if your application loses the refresh token, the user will need to repeat the OAuth 2.0 consent flow so that your application can obtain a new refresh token.

The following snippet shows a sample response:

{
  "access_token": "1/fFAGRNJru1FTz70BzhT3Zg",
  "expires_in": 3920,
  "token_type": "Bearer",
  "scope": "https://www.googleapis.com/auth/drive.metadata.readonly https://www.googleapis.com/auth/calendar.readonly",
  "refresh_token": "1//xEoDL4iW3cxlI7yDbSRFYNG01kVKM2C-259HOF2aQbI"
}

Note: Your application should ignore any unrecognized fields included in the response.

Step 6: Check which scopes users granted

When requesting multiple scopes at once, users may not grant all scopes your app requests. Your app should always check which scopes were granted by the user and handle any denial of scopes by disabling relevant features. Review How to handle granular permissions for more information.

To check whether the user has granted your application access to a particular scope, exam the scope field in the access token response. The scopes of access granted by the access_token expressed as a list of space-delimited, case-sensitive strings.

For example, the following sample access token response indicates that the user has granted your application access to the read-only Drive activity and Calendar events permissions:

  {
    "access_token": "1/fFAGRNJru1FTz70BzhT3Zg",
    "expires_in": 3920,
    "token_type": "Bearer",
    "scope": "https://www.googleapis.com/auth/drive.metadata.readonly https://www.googleapis.com/auth/calendar.readonly",
    "refresh_token": "1//xEoDL4iW3cxlI7yDbSRFYNG01kVKM2C-259HOF2aQbI"
  }

Calling Google APIs

After your application obtains an access token, you can use the token to make calls to a Google API on behalf of a given user account if the scope(s) of access required by the API have been granted. To do this, include the access token in a request to the API by including either an access_token query parameter or an Authorization HTTP header Bearer value. When possible, the HTTP header is preferable, because query strings tend to be visible in server logs. In most cases you can use a client library to set up your calls to Google APIs (for example, when calling the Drive Files API).

You can try out all the Google APIs and view their scopes at the OAuth 2.0 Playground.

HTTP GET examples

A call to the drive.files endpoint (the Drive Files API) using the Authorization: Bearer HTTP header might look like the following. Note that you need to specify your own access token:

GET /drive/v2/files HTTP/1.1
Host: www.googleapis.com
Authorization: Bearer access_token

Here is a call to the same API for the authenticated user using the access_token query string parameter:

GET https://www.googleapis.com/drive/v2/files?access_token=access_token

curl examples

You can test these commands with the curl command-line application. Here's an example that uses the HTTP header option (preferred):

curl -H "Authorization: Bearer access_token" https://www.googleapis.com/drive/v2/files

Or, alternatively, the query string parameter option:

curl https://www.googleapis.com/drive/v2/files?access_token=access_token

Refreshing an access token

Access tokens periodically expire and become invalid credentials for a related API request. You can refresh an access token without prompting the user for permission (including when the user is not present) if you requested offline access to the scopes associated with the token.

To refresh an access token, your application sends an HTTPS POST request to Google's authorization server (https://oauth2.googleapis.com/token) that includes the following parameters:

Fields
client_id	The client ID obtained from the API Console.
client_secret	The client secret obtained from the API Console. (The client_secret is not applicable to requests from clients registered as Android, iOS, or Chrome applications.)
grant_type	As defined in the OAuth 2.0 specification, this field's value must be set to refresh_token.
refresh_token	The refresh token returned from the authorization code exchange.

The following snippet shows a sample request:

POST /token HTTP/1.1
Host: oauth2.googleapis.com
Content-Type: application/x-www-form-urlencoded

client_id=your_client_id&
client_secret=your_client_secret&
refresh_token=refresh_token&
grant_type=refresh_token

As long as the user has not revoked the access granted to the application, the token server returns a JSON object that contains a new access token. The following snippet shows a sample response:

{
  "access_token": "1/fFAGRNJru1FTz70BzhT3Zg",
  "expires_in": 3920,
  "scope": "https://www.googleapis.com/auth/drive.metadata.readonly https://www.googleapis.com/auth/calendar.readonly",
  "token_type": "Bearer"
}

Note that there are limits on the number of refresh tokens that will be issued; one limit per client/user combination, and another per user across all clients. You should save refresh tokens in long-term storage and continue to use them as long as they remain valid. If your application requests too many refresh tokens, it may run into these limits, in which case older refresh tokens will stop working.

Revoking a token

In some cases a user may wish to revoke access given to an application. A user can revoke access by visiting Account Settings. See the Remove site or app access section of the Third-party sites & apps with access to your account support document for more information.

It is also possible for an application to programmatically revoke the access given to it. Programmatic revocation is important in instances where a user unsubscribes, removes an application, or the API resources required by an app have significantly changed. In other words, part of the removal process can include an API request to ensure the permissions previously granted to the application are removed.

To programmatically revoke a token, your application makes a request to https://oauth2.googleapis.com/revoke and includes the token as a parameter:

curl -d -X -POST --header "Content-type:application/x-www-form-urlencoded" \
        https://oauth2.googleapis.com/revoke?token={token}

The token can be an access token or a refresh token. If the token is an access token and it has a corresponding refresh token, the refresh token will also be revoked.

If the revocation is successfully processed, then the HTTP status code of the response is 200. For error conditions, an HTTP status code 400 is returned along with an error code.

Note: Following a successful revocation response, it might take some time before the revocation has full effect.

App redirect methods

Custom URI scheme (Android, iOS, UWP)

Custom URI schemes are a form of deeplinking that use a custom-defined scheme to open your app.

Important: Custom URI schemes are no longer supported on new Chrome apps and are disabled by default on new Android clients due to the risk of app impersonation.

Alternative to using custom URI schemes on Android

Use the Google Sign-In for Android SDK which delivers the OAuth 2.0 response directly to your app, eliminating the need for a redirect URI.

How to migrate to the Google Sign-In for Android SDK

If you use a custom scheme for your OAuth integration on Android, you would need to complete the following actions to fully migrate to using the recommended Google Sign-In for Android SDK:

1. Update your code to use the Google Sign-In SDK.
2. Disable support for custom scheme in the Google API Console.

Note: You should complete and deploy your code updates (accounting for adoption time across your user base or older devices) before disabling support for custom schemes in the Google API Console to avoid users getting an invalid_request error message when they try to use your app.

Follow the below steps to migrate to the Google Sign-In Android SDK:

1. Update your code to use the Google Sign-In Android SDK:
   1. Examine your code to identify where you are sending a request to Google's OAuth 2.0 server; if using a custom scheme, your request would look like the below:

        https://accounts.google.com/o/oauth2/v2/auth?
        scope=<SCOPES>&
        response_type=code&
        &state=<STATE>&
        redirect_uri=com.example.app:/oauth2redirect&
        client_id=<CLIENT_ID>
        

      com.example.app:/oauth2redirect is the custom scheme redirect URI in the above example. See the redirect_uri parameter definition for more details about the format of the custom URI scheme value.
   2. Make note of the scope and client_id request parameters which you would need to configure the Google Sign-In SDK.
      Note: If you are using a third-party library, review the library's configuration file to find these information.
   3. Follow the Start Integrating Google Sign-In into Your Android App instructions to set up the SDK. You can skip the Get your backend server's OAuth 2.0 client ID step as you would re-use the client_id you retrieved from the previous step.
   4. Follow the Enabling Server-Side API access instructions. This includes the following steps:
      1. Use the getServerAuthCode method to retrieve an auth code for the scopes you are requesting permission for.
      2. Send the auth code to your app's backend to exchange it for an access & refresh token.
      3. Use the retrieved access token to make calls to Google APIs on behalf of the user.
      Note: If your application does not require offline access, follow these instructions instead to request client-side API access.
2. Disable support for custom scheme in the Google API Console:
   1. Go to your OAuth 2.0 credentials list and select your Android client.
   2. Navigate to the Advanced Settings section, uncheck the Enable Custom URI Scheme checkbox, and click Save to disable custom URI scheme support.

Enable custom URI scheme

If the recommended alternative does not work for you, you can enable custom URI schemes for your Android client by following the below instructions:

1. Go to your OAuth 2.0 credentials list and select your Android client.
2. Navigate to the Advanced Settings section, check the Enable Custom URI Scheme checkbox, and click Save to enable custom URI scheme support.

Alternative to using custom URI schemes on Chrome apps

Use the Chrome Identity API which delivers the OAuth 2.0 response directly to your app, eliminating the need for a redirect URI.

Loopback IP address (macOS, Linux, Windows desktop)

Important: The loopback IP address redirect option is DEPRECATED for the Android, Chrome app, and iOS OAuth client types. Review the loopback IP address migration guide for instructions on how to migrate to a supported alternative.

To receive the authorization code using this URL, your application must be listening on the local web server. That is possible on many, but not all, platforms. However, if your platform supports it, this is the recommended mechanism for obtaining the authorization code.

When your app receives the authorization response, for best usability it should respond by displaying an HTML page that instructs the user to close the browser and return to your app.

Recommended usage	macOS, Linux, and Windows desktop (but not Universal Windows Platform) apps
Form values	Set the application type to Desktop app.

Note: See the redirect_uri parameter definition for more information about the loopback IP address. It is also possible to use localhost in place of the loopback IP, but this configuration may cause issues with client firewalls. Most, but not all, firewalls allow loopback communication.

Manual copy/paste (Deprecated)

Important: The manual copy/paste option, also referred to as an out of band (OOB) redirect method, is no longer supported. Review the OOB migration guide for instructions on how to migrate to a secure alternative.

Protect your apps

Verify app ownership (Android, Chrome)

You can verify ownership of your application to reduce the risk of app impersonation.

Android

Note: Android app ownership verification is only available for Google Play apps.

To complete the verification process, you can use your Google Play Developer Account if you have one and your app is registered on the Google Play Console. The following requirements must be met for a successful verification:

• You must have a registered application in the Google Play Console with the same package name and SHA-1 signing certificate fingerprint as the Android OAuth client you are completing the verification for.
• You must have Admin permission for the app in the Google Play Console. Learn more about access management in the Google Play Console.

In the Verify App Ownership section of the Android client, click the Verify Ownership button to complete the verification process.

If the verification is successful, a notification will be displayed to confirm the success of the verification process. Otherwise, an error prompt will be shown.

To fix a failed verification, try the following:

• Make sure the app you are verifying is a registered app in the Google Play Console.
• Make sure you have Admin permission for the app in the Google Play Console.

Chrome

To complete the verification process, you would use your Chrome Web Store Developer account. The following requirements must be met for a successful verification:

• You must have a registered item in the Chrome Web Store Developer Dashboard with the same item ID as the Chrome Extension OAuth client you are completing the verification for.
• You must be a publisher for the Chrome Web Store item. Learn more about access management in the Chrome Web Store Developer Dashboard.

In the Verify App Ownership section of the Chrome Extension client, click the Verify Ownership button to complete the verification process.

Note: Wait a few minutes before completing the verification process after granting access to your account.

If the verification is successful, a notification will be displayed to confirm the success of the verification process. Otherwise, an error prompt will be shown.

To fix a failed verification, try the following:

• Make sure there is a registered item in the Chrome Web Store Developer Dashboard with the same item ID as the Chrome Extension OAuth client you are completing the verification for.
• Make sure you are a publisher for the app, that is, you must either be the individual publisher of the app or a member of the group publisher of the app. Learn more about access management in the Chrome Web Store Developer Dashboard.
• If you just updated your group publisher list, verify that the group publisher membership list is synced in the Chrome Web Store Developer Dashboard. Learn more about syncing your publisher membership list.

App Check (iOS only)

The App Check feature helps safeguard your iOS applications from unauthorized usage by using Apple's App Attest service to verify that requests made to Google OAuth 2.0 endpoints originate from your authentic applications. This helps to reduce the risk of app impersonation.

Enable App Check for your iOS Client

The following requirements must be met to successfully enable App Check for your iOS client:

• You must specify a team ID for your iOS client.
• You must not use a wildcard in your bundle ID since it can resolve to more than one app. This means that the bundle ID must not include the asterisk (*) symbol.

Warning: When App Check is enabled, you won't be able to edit your OAuth client bundle ID without creating a new client. Before creating your iOS client or enabling App Check, verify that you are using the correct bundle ID. Updating your bundle ID for an existing project can result in a broken experience for users of your apps if you are using the bundle ID as a redirect URI.

To enable App Check, turn on the Protect your OAuth client from abuse with Firebase App Check toggle button in the edit view of your iOS client.

After enabling App Check, you will start seeing metrics related to OAuth requests from your client in the edit view of the OAuth client. Requests from unverified sources won't be blocked until you enforce App Check. The information in the metrics monitoring page can help you determine when to start enforcement.

You might see errors related to the App Check feature when enabling App Check for your iOS app. To fix these errors, try the following:

• Verify that the bundle ID and team ID you specified are valid.
• Verify that you are not using a wildcard for the bundle ID.

Enforce App Check for your iOS Client

Enabling App Check for your app does not automatically block unrecognized requests. To enforce this protection, go to the edit view of your iOS client. There, you will see App Check metrics to the right of the page under the Google Identity for iOS section. 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.

Review these metrics to understand how enforcing App Check will affect your users.

To enforce App Check, click the ENFORCE button and confirm your choice. Once enforcement is active, all unverified requests from your client will be rejected.

Note: after you enable enforcement, it can take up to 15 minutes for the changes to take effect.

Unenforce App Check for your iOS Client

Unenforcing App Check for your app will stop enforcement and will allow all requests from your client to Google OAuth 2.0 endpoints, including unverified requests.

To unenforce App Check for your iOS client, navigate to the edit view of the iOS client and click the UNENFORCE button and confirm your choice.

Note: after unenforcing App Check, it can take up to 15 minutes for the changes to take effect.

Disable App Check for your iOS Client

Disabling App Check for your app will stop all App Check monitoring and enforcement. Consider unenforcing App Check instead so you can continue monitoring metrics for your client.

To disable App Check for your iOS client, navigate to the edit view of the iOS client and turn off the Protect your OAuth client from abuse with Firebase App Check toggle button.

Note: after disabling App Check, it can take up to 15 minutes for the changes to take effect.

Further Reading

The IETF Best Current Practice OAuth 2.0 for Native Apps establishes many of the best practices documented here.

Implementing Cross-Account Protection

An additional step you should take to protect your users' accounts is implementing Cross-Account Protection by utilizing Google's Cross-Account Protection Service. This service lets you subscribe to security event notifications which provide information to your application about major changes to the user account. You can then use the information to take action depending on how you decide to respond to events.

Some examples of the event types sent to your app by Google's Cross-Account Protection Service are:

• https://schemas.openid.net/secevent/risc/event-type/sessions-revoked
• https://schemas.openid.net/secevent/oauth/event-type/token-revoked
• https://schemas.openid.net/secevent/risc/event-type/account-disabled

See the Protect user accounts with Cross-Account Protection page for more information on how to implement Cross Account Protection and for the full list of available events.