4xx Client errors
401 Unauthorized
Authentication is needed and was missing or wrong.
Common causes
- No API key or token, or an expired one.
- Wrong username or password for basic auth.
How to fix it
- Send valid credentials, usually an Authorization header.
- Refresh expired tokens.
- To monitor a protected endpoint, add the auth header to the monitor.
Find out the moment your site returns 401
Spot Downtime monitors count this as down and alert you, since visitors see an error. (The public “Is it down?” checker treats 4xx answers from big sites as online, because many refuse automated requests.)