401 Unauthorized — Causes & Fix
HTTP 401 (Unauthorized) means the request requires authentication that is missing or invalid — you are not logged in or your credentials/token were rejected.
- Applies to
- Any website or web server (HTTP standard)
- Time to fix
- 5–30 minutes
What it means
Causes include not being logged in, an expired session/token, wrong credentials, or a missing Authorization header. HTTP status 401 is defined in RFC 9110 (HTTP Semantics). This is a client-side (4xx) error — the request itself had a problem, so the fix is usually on the requester's side or in how the server validates the request.
Symptoms
- "401 Unauthorized" on a protected page or API
- Prompted to log in, or the API rejects the token
How to fix it
- 1
Log in / refresh credentials
1. As a user: log in again — your session may have expired.
- 2
Send valid auth (developers)
1. Include a valid Authorization header/token. 2. Refresh an expired token and confirm the credentials are correct.
Frequently asked questions
401 vs 403 — what's the difference?
401 means "you are not authenticated" (log in). 403 means "you are authenticated but not allowed" — logging in won't help.
Last updated July 20, 2026
Guidance only — always consult a qualified professional or the official service manual before carrying out repairs.