Fixing “ACCESS_TOKEN_SCOPE_INSUFFICIENT” in Gmail API: A Guide for Java Developers

Encountering the ACCESS_TOKEN_SCOPE_INSUFFICIENT error in the Gmail API? This issue occurs when your OAuth token lacks the required permissions (scopes) for a specific operation, such as reading or sending emails. This guide will walk you through practical solutions to resolve this error and ensure your application has the correct access.

Understanding the Error

The error message “Request had insufficient authentication scopes” means your OAuth token is missing the necessary Gmail API permissions. Common use cases and their required scopes include:

• Reading emails → https://www.googleapis.com/auth/gmail.readonly or https://www.googleapis.com/auth/gmail.modify
• Sending emails → https://www.googleapis.com/auth/gmail.send

If your token lacks these scopes, API requests like messages.list() or messages.get() will fail.

Solution 1: Update OAuth Scopes in Your Code

Step 1: Define the Correct Scopes

Ensure your Java application includes the required scopes when initializing the Gmail API client.

❌ Incorrect Scopes:

private static final List<String> SCOPES =   
    Collections.singletonList(GmailScopes.MAIL_GOOGLE_COM); // Only allows sending emails  

✅ Correct Scopes:

private static final List<String> SCOPES =   
    Arrays.asList(GmailScopes.GMAIL_READONLY, GmailScopes.GMAIL_SEND);  

Step 2: Delete Cached Tokens

OAuth tokens do not update automatically when you modify scopes. Delete any previously stored tokens:

rm -rf tokens/  

Step 3: Reauthorize Your App

Run your application again and grant permissions when prompted. This ensures the new token includes the updated scopes.

Solution 2: Check Google Cloud Console (GCP) Settings

Step 1: Verify OAuth Consent Screen Scopes

1. Open the Google Cloud Console.
2. Navigate to APIs & Services > OAuth Consent Screen.
3. Under Scopes for Google APIs, ensure the necessary scopes (e.g., .../auth/gmail.readonly) are listed.

Step 2: Update credentials.json

If you modify scopes in the OAuth consent screen:

1. Re-download the credentials.json file from APIs & Services > Credentials.
2. Replace the old file in your project.

Solution 3: Debug Token Scopes

To check which scopes your token actually has, use this debug code:

Credential credential = getCredentials(HTTP_TRANSPORT);  
System.out.println("Granted Scopes: " + credential.getAccessToken().getScope());  

If the output does not include https://www.googleapis.com/auth/gmail.readonly, your token is missing required permissions.

Solution 4: Ensure Correct API Usage

Example: Fetching Emails

Make sure you’re using the right Gmail API methods:

ListMessagesResponse response = service.users().messages()  
    .list("me")  
    .setQ("is:unread") // Optional filter  
    .execute();  

List<Message> messages = response.getMessages();  

If your application still fails, double-check that your OAuth scopes match the API methods being used.

Common Pitfalls & Fixes

1. Cached Tokens Persisting → Delete stored tokens (rm -rf tokens/) before reauthorizing.
2. Outdated credentials.json → Download and replace with the latest version from Google Cloud Console.
3. Typos in Scopes → Ensure the scope strings are correct and match Gmail API documentation.

Conclusion

To resolve the ACCESS_TOKEN_SCOPE_INSUFFICIENT error in Gmail API:
✅ Define the correct OAuth scopes (e.g., GmailScopes.GMAIL_READONLY).
✅ Verify your Google Cloud project’s consent screen settings.
✅ Delete old tokens and reauthorize your application.

By following these steps, your Java application will gain the required permissions to interact with Gmail effectively.

Need More Help?

• Gmail API Scopes Documentation
• Google Cloud OAuth Guide

Meta Description: “Fix Gmail API’s ACCESS_TOKEN_SCOPE_INSUFFICIENT error in Java. Learn how to update OAuth scopes, refresh tokens, and configure Google Cloud settings.”

Keywords: Gmail API insufficient scopes, ACCESS_TOKEN_SCOPE_INSUFFICIENT Java, Gmail.readonly scope, Gmail API permissions, OAuth token troubleshooting, Java Gmail API authentication.