Q: What causes REST API Call Returning 401 Unauthorized in ServiceNow?

Outbound REST Message credentials are incorrect or expired — Check the REST Message record under System Web Services > Outbound > REST Message. Look at the Authentication tab - Basic Auth credentials may be wrong or OAuth access token has expired. Inbound user lacks rest_service role — Navigate to User Administration > Users and check if the authenticating user has the rest_service role assigned. Without this role, all REST API calls will return 401. User account is locked or password expired — In the sys_user table, check the 'Locked out' field and 'Password needs reset' field for the authenticating user. Also verify 'Active' is true. Basic Auth header not being sent in outbound call — Check the REST Message HTTP Headers tab and verify the Authorization header is present. Also check if 'Use basic auth' is enabled in the Authentication section. OAuth Application Registry misconfigured for inbound calls — Navigate to System OAuth > Application Registry and verify the OAuth provider configuration matches what the client is sending. Check redirect URI and client credentials. IP address blocked by Security Rules — Check System Security > Security Rules for any IP address restrictions. Also verify System Properties > Security has 'glide.authenticate.sso.reject.invalid_ip' set appropriately.

Question 1

What causes REST API Call Returning 401 Unauthorized in ServiceNow?

Accepted Answer

Outbound REST Message credentials are incorrect or expiredhigh likelihood

Check the REST Message record under System Web Services > Outbound > REST Message. Look at the Authentication tab - Basic Auth credentials may be wrong or OAuth access token has expired.

Inbound user lacks rest_service rolehigh likelihood

Navigate to User Administration > Users and check if the authenticating user has the rest_service role assigned. Without this role, all REST API calls will return 401.

User account is locked or password expiredmedium likelihood

In the sys_user table, check the 'Locked out' field and 'Password needs reset' field for the authenticating user. Also verify 'Active' is true.

Basic Auth header not being sent in outbound callmedium likelihood

Check the REST Message HTTP Headers tab and verify the Authorization header is present. Also check if 'Use basic auth' is enabled in the Authentication section.

OAuth Application Registry misconfigured for inbound callsmedium likelihood

Navigate to System OAuth > Application Registry and verify the OAuth provider configuration matches what the client is sending. Check redirect URI and client credentials.

IP address blocked by Security Ruleslow likelihood

Check System Security > Security Rules for any IP address restrictions. Also verify System Properties > Security has 'glide.authenticate.sso.reject.invalid_ip' set appropriately.

Question 2

How do you fix REST API Call Returning 401 Unauthorized in ServiceNow?

Accepted Answer

How to fix it Navigate to System Web Services > Outbound > REST Message and open your REST Message record. Click the Authentication tab and verify the authentication type matches what your target API expects (Basic, OAuth 2.0, etc.). If using Basic Auth, verify the User name and Password fields contain the correct credentials for the target system. If using OAuth 2.0, check if the Access token field is populated and click Get OAuth Token to refresh if needed. Navigate to User Administration > Users and search for the user account making inbound REST calls to your instance. Open the user record and verify Active is checked, Locked out is unchecked, and Password needs reset is unchecked. Click the Roles tab and verify rest_service appears in the roles list. If not, click Edit and add it. For outbound calls, check the HTTP Headers tab on your REST Message and verify an Authorization header exists if using manual Basic Auth. Navigate to System OAuth > Application Registry if using OAuth for inbound calls and verify the client ID, secret, and redirect URI match your client application. Check System Logs > System Log > All and filter by Source contains REST to see detailed authentication failure messages. If the issue persists, navigate to System Security > Security Rules and check for IP address restrictions that might block your client.

Question 3

How do you prevent REST API Call Returning 401 Unauthorized in ServiceNow?

Accepted Answer

Set up credential aliases in System Web Services > Outbound > Credential Store to avoid hardcoding passwords in REST Messages. Create a dedicated integration user with only the rest_service role and required table permissions instead of using admin accounts. Configure OAuth token refresh automation by setting up a scheduled job that calls the token endpoint before expiration. Enable REST API logging in System Properties by setting glide.rest.log_level to info to capture authentication details for troubleshooting. Document your REST Message authentication configuration in the Description field including token refresh schedules and credential rotation dates.

REST API Call Returning 401 Unauthorized in ServiceNow

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