lightmy.dayINSTANT ANSWERS

Client error

HTTP 401: Unauthorized

HTTP 401 means authentication is required or failed.

Meaning

The client must authenticate before the server can return the protected resource.

Common causes

Missing credentials, expired tokens, invalid API keys, or failed login sessions can cause it.

What to check

Send valid credentials, refresh the token, or check the WWW-Authenticate response header.

Example response

HTTP/1.1 401 Unauthorized

References

Registry: IANA HTTP Status Code Registry
Spec: RFC 9110 §15.5.2
Guide: MDN 401 Unauthorized

Related HTTP status codes

Nearby codes often answer the next debugging question.

400 Bad RequestHTTP 400 means the server could not understand the request.403 ForbiddenHTTP 403 means the server understood the request but refuses access.404 Not FoundHTTP 404 means the server could not find the requested resource.