Question 1

What does HTTP 401 Unauthorized mean?

Accepted Answer

The request requires user authentication. The client must provide valid credentials (such as a token or username/password) to access the resource. Despite the name, this is about authentication, not authorization.

Question 2

What causes an HTTP 401 Unauthorized error?

Accepted Answer

Missing or expired authentication token. Invalid API key or credentials. Session has timed out and user needs to re-login. Authorization header format is incorrect.

Question 3

How do I fix HTTP 401 Unauthorized?

Accepted Answer

Include a valid Authorization header with your request Refresh expired tokens or re-authenticate Check that credentials are correct and not revoked Verify the authentication scheme (Bearer, Basic, etc.)

Question 4

Is HTTP 401 a client error or server error?

Accepted Answer

401 is a Client Error response (4xx). The error is on the client side — the request contains bad syntax, refers to a missing resource, or lacks proper authentication. The server cannot or will not process the request.

Question 5

When does a server return HTTP 401?

Accepted Answer

A server returns HTTP 401 Unauthorized when: missing or expired authentication token. This code belongs to the Client Error category (4xx).

HTTP 401 Unauthorized— What It Means, Causes & How to Fix It

Common Causes

How to Fix

Example

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Commonly Referenced Status Codes

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