Verify the Google ID token on your server side

After Google returns an ID token, it's submitted by an HTTP POST method request, with the parameter name credential , to your login endpoint.

The following is an example in the Python language that shows the usual steps to validate and consume the ID token:

Verify the Cross-Site Request Forgery (CSRF) token. When you submit credentials to your login endpoint, we use the double-submit-cookie pattern to prevent CSRF attacks. Before each submission, we generate a token. Then, the token is put into both the cookie and the post body, as shown in the following code example:

  csrf_token_cookie 
 = 
 self 
 . 
 request 
 . 
 cookies 
 . 
 get 
 ( 
 'g_csrf_token' 
 ) 
 if 
 not 
 csrf_token_cookie 
 : 
 webapp2 
 . 
 abort 
 ( 
 400 
 , 
 'No CSRF token in Cookie.' 
 ) 
 csrf_token_body 
 = 
 self 
 . 
 request 
 . 
 get 
 ( 
 'g_csrf_token' 
 ) 
 if 
 not 
 csrf_token_body 
 : 
 webapp2 
 . 
 abort 
 ( 
 400 
 , 
 'No CSRF token in post body.' 
 ) 
 if 
 csrf_token_cookie 
 != 
 csrf_token_body 
 : 
 webapp2 
 . 
 abort 
 ( 
 400 
 , 
 'Failed to verify double submit cookie.' 
 )

Verify the ID token.

To verify that the token is valid, ensure that the following criteria are satisfied:

The ID token is properly signed by Google. Use Google's public keys (available in JWK or PEM format) to verify the token's signature. These keys are regularly rotated; examine the Cache-Control header in the response to determine when you should retrieve them again.
The value of aud in the ID token is equal to one of your app's client IDs. This check is necessary to prevent ID tokens issued to a malicious app being used to access data about the same user on your app's backend server.
The value of iss in the ID token is equal to accounts.google.com or https://accounts.google.com .
The expiry time ( exp ) of the ID token has not passed.
If you need to validate that the ID token represents a Google Workspace or Cloud organization account, you can check the hd claim, which indicates the hosted domain of the user. This must be used when restricting access to a resource to only members of certain domains. The absence of this claim indicates that the account does not belong to a Google hosted domain.

Using the email , email_verified and hd fields, you can determine if Google hosts and is authoritative for an email address. In the cases where Google is authoritative, the user is known to be the legitimate account owner, and you may skip password or other challenge methods.

Cases where Google is authoritative:

email has a @gmail.com suffix, this is a Gmail account.
email_verified is true and hd is set, this is a Google Workspace account.

Users may register for Google Accounts without using Gmail or Google Workspace. When email does not contain a @gmail.com suffix and hd is absent, Google is not authoritative and password or other challenge methods are recommended to verify the user. email_verified can also be true as Google initially verified the user when the Google account was created, however ownership of the third party email account may have since changed.

Rather than writing your own code to perform these verification steps, we strongly recommend using a Google API client library for your platform, or a general-purpose JWT library. For development and debugging, you can call our tokeninfo validation endpoint.

Using a Google API Client Library

Using one of the Google API Client Libraries (e.g. Java , Node.js , PHP , Python ) is the recommended way to validate Google ID tokens in a production environment.

Java

To validate an ID token in Java, use the GoogleIdTokenVerifier object. For example:

 import 
  
 com.google.api.client.googleapis.auth.oauth2.GoogleIdToken 
 ; 
 import 
  
 com.google.api.client.googleapis.auth.oauth2.GoogleIdToken.Payload 
 ; 
 import 
  
 com.google.api.client.googleapis.auth.oauth2.GoogleIdTokenVerifier 
 ; 
 ... 
 GoogleIdTokenVerifier 
 verifier 
 = 
 new 
 GoogleIdTokenVerifier 
 . 
 Builder 
 ( 
 transport 
 , 
 jsonFactory 
 ) 
 // 
 Specify 
 the 
 WEB_CLIENT_ID 
 of 
 the 
 app 
 that 
 accesses 
 the 
 backend 
 : 
 . 
 setAudience 
 ( 
 Collections 
 . 
 singletonList 
 ( 
 WEB_CLIENT_ID 
 )) 
 // 
 Or 
 , 
 if 
 multiple 
 clients 
 access 
 the 
 backend 
 : 
 //. 
 setAudience 
 ( 
 Arrays 
 . 
 asList 
 ( 
 WEB_CLIENT_ID_1 
 , 
 WEB_CLIENT_ID_2 
 , 
 WEB_CLIENT_ID_3 
 )) 
 . 
 build 
 (); 
 // 
 ( 
 Receive 
 idTokenString 
 by 
 HTTPS 
 POST 
 ) 
 GoogleIdToken 
 idToken 
 = 
 verifier 
 . 
 verify 
 ( 
 idTokenString 
 ); 
 if 
 ( 
 idToken 
 != 
 null 
 ) 
 { 
 Payload 
 payload 
 = 
 idToken 
 . 
 getPayload 
 (); 
 // 
 Print 
 user 
 identifier 
 String 
 userId 
 = 
 payload 
 . 
 getSubject 
 (); 
 System 
 . 
 out 
 . 
 println 
 ( 
 "User ID: " 
 + 
 userId 
 ); 
 // 
 Get 
 profile 
 information 
 from 
  
 payload 
 String 
 email 
 = 
 payload 
 . 
 getEmail 
 (); 
 boolean 
 emailVerified 
 = 
 Boolean 
 . 
 valueOf 
 ( 
 payload 
 . 
 getEmailVerified 
 ()); 
 String 
 name 
 = 
 ( 
 String 
 ) 
 payload 
 . 
 get 
 ( 
 "name" 
 ); 
 String 
 pictureUrl 
 = 
 ( 
 String 
 ) 
 payload 
 . 
 get 
 ( 
 "picture" 
 ); 
 String 
 locale 
 = 
 ( 
 String 
 ) 
 payload 
 . 
 get 
 ( 
 "locale" 
 ); 
 String 
 familyName 
 = 
 ( 
 String 
 ) 
 payload 
 . 
 get 
 ( 
 "family_name" 
 ); 
 String 
 givenName 
 = 
 ( 
 String 
 ) 
 payload 
 . 
 get 
 ( 
 "given_name" 
 ); 
 // 
 Use 
 or 
 store 
 profile 
 information 
 // 
 ... 
 } 
 else 
 { 
 System 
 . 
 out 
 . 
 println 
 ( 
 "Invalid ID token." 
 ); 
 }

The GoogleIdTokenVerifier.verify() method verifies the JWT signature, the aud claim, the iss claim, and the exp claim.

If you need to validate that the ID token represents a Google Workspace or Cloud organization account, you can verify the hd claim by checking the domain name returned by the Payload.getHostedDomain() method. The domain of the email claim is insufficient to ensure that the account is managed by a domain or organization.

Node.js

To validate an ID token in Node.js, use the Google Auth Library for Node.js . Install the library:

npm install google-auth-library --save

Then, call the verifyIdToken() function. For example:

 const 
  
 { 
 OAuth2Client 
 } 
  
 = 
  
 require 
 ( 
 'google-auth-library' 
 ); 
 const 
  
 client 
  
 = 
  
 new 
  
 OAuth2Client 
 (); 
 async 
  
 function 
  
 verify 
 () 
  
 { 
  
 const 
  
 ticket 
  
 = 
  
 await 
  
 client 
 . 
 verifyIdToken 
 ({ 
  
 idToken 
 : 
  
 token 
 , 
  
 audience 
 : 
  
 WEB_CLIENT_ID 
 , 
  
 // 
  
 Specify 
  
 the 
  
 WEB_CLIENT_ID 
  
 of 
  
 the 
  
 app 
  
 that 
  
 accesses 
  
 the 
  
 backend 
  
 // 
  
 Or 
 , 
  
 if 
  
 multiple 
  
 clients 
  
 access 
  
 the 
  
 backend 
 : 
  
 // 
 [ 
 WEB_CLIENT_ID_1 
 , 
  
 WEB_CLIENT_ID_2 
 , 
  
 WEB_CLIENT_ID_3 
 ] 
  
 }); 
  
 const 
  
 payload 
  
 = 
  
 ticket 
 . 
 getPayload 
 (); 
  
 const 
  
 userid 
  
 = 
  
 payload 
 [ 
 'sub' 
 ]; 
  
 // 
  
 If 
  
 the 
  
 request 
  
 specified 
  
 a 
  
 Google 
  
 Workspace 
  
 domain 
 : 
  
 // 
  
 const 
  
 domain 
  
 = 
  
 payload 
 [ 
 'hd' 
 ]; 
 } 
 verify 
 () 
 . 
 catch 
 ( 
 console 
 . 
 error 
 );

The verifyIdToken function verifies the JWT signature, the aud claim, the exp claim, and the iss claim.

If you need to validate that the ID token represents a Google Workspace or Cloud organization account, you can check the hd claim, which indicates the hosted domain of the user. This must be used when restricting access to a resource to only members of certain domains. The absence of this claim indicates that the account does not belong to a Google hosted domain.

PHP

To validate an ID token in PHP, use the Google API Client Library for PHP . Install the library (for example, using Composer):

composer require google/apiclient

Then, call the verifyIdToken() function. For example:

 require_once 
  
 'vendor/autoload.php' 
 ; 
 // 
  
 Get 
  
 $ 
 id_token 
  
 via 
  
 HTTPS 
  
 POST 
 . 
 $ 
 client 
  
 = 
  
 new 
  
 Google_Client 
 ([ 
 'client_id' 
  
 => 
  
 $ 
 WEB_CLIENT_ID 
 ]); 
  
 // 
  
 Specify 
  
 the 
  
 WEB_CLIENT_ID 
  
 of 
  
 the 
  
 app 
  
 that 
  
 accesses 
  
 the 
  
 backend 
 $ 
 payload 
  
 = 
  
 $ 
 client 
 -> 
 verifyIdToken 
 ( 
 $ 
 id_token 
 ); 
 if 
  
 ( 
 $ 
 payload 
 ) 
  
 { 
  
 $ 
 userid 
  
 = 
  
 $ 
 payload 
 [ 
 'sub' 
 ]; 
  
 // 
  
 If 
  
 the 
  
 request 
  
 specified 
  
 a 
  
 Google 
  
 Workspace 
  
 domain 
  
 //$ 
 domain 
  
 = 
  
 $ 
 payload 
 [ 
 'hd' 
 ]; 
 } 
  
 else 
  
 { 
  
 // 
  
 Invalid 
  
 ID 
  
 token 
 }

The verifyIdToken function verifies the JWT signature, the aud claim, the exp claim, and the iss claim.

Python

To validate an ID token in Python, use the verify_oauth2_token function. For example:

 from 
  
 google.oauth2 
  
 import 
 id_token 
 from 
  
 google.auth.transport 
  
 import 
 requests 
 # (Receive token by HTTPS POST) 
 # ... 
 try 
 : 
 # Specify the WEB_CLIENT_ID of the app that accesses the backend: 
 idinfo 
 = 
 id_token 
 . 
 verify_oauth2_token 
 ( 
 token 
 , 
 requests 
 . 
 Request 
 (), 
 WEB_CLIENT_ID 
 ) 
 # Or, if multiple clients access the backend server: 
 # idinfo = id_token.verify_oauth2_token(token, requests.Request()) 
 # if idinfo['aud'] not in [WEB_CLIENT_ID_1, WEB_CLIENT_ID_2, WEB_CLIENT_ID_3]: 
 #     raise ValueError('Could not verify audience.') 
 # If the request specified a Google Workspace domain 
 # if idinfo['hd'] != DOMAIN_NAME: 
 #     raise ValueError('Wrong domain name.') 
 # ID token is valid. Get the user's Google Account ID from the decoded token. 
 userid 
 = 
 idinfo 
 [ 
 'sub' 
 ] 
 except 
 ValueError 
 : 
 # Invalid token 
 pass

The verify_oauth2_token function verifies the JWT signature, the aud claim, and the exp claim. You must also verify the hd claim (if applicable) by examining the object that verify_oauth2_token returns. If multiple clients access the backend server, also manually verify the aud claim.

Once the token's validity is confirmed, you can use the information in the Google ID token to correlate the account status of your site:
- An unregistered user:You can show a sign-up user interface (UI) that allows the user to provide additional profile information, if required. It also allows the user to silently create the new account and a logged-in user session.
- An existing account that already exists in your site:You can show a web page that allows the end user to input their password and link the legacy account with their Google credentials. This confirms that the user has access to the existing account.
- A returning federated user:You can silently sign the user in.

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Using a Google API Client Library

Verify the Google ID token on your server side