What is the HTTP Error Code Associated with Authentication issues in a Web Browser Client?

The HTTP error code most commonly associated with authentication issues in a web browser client is 401 Unauthorized. This status code indicates that the request requires user authentication, but the client has either not provided valid credentials or has not provided any credentials at all.

When a server responds with a 401 error, it typically includes a "WWW-Authenticate" header, prompting the client to supply appropriate credentials, such as a username and password, for access. If the client does not provide valid credentials in subsequent requests, the 401 error will continue to be returned.

Additionally, the 403 Forbidden error code can appear in authentication-related scenarios. Unlike 401, 403 indicates that the server understood the request and the credentials provided, but the user does not have the necessary permissions to access the resource, even if they are authenticated.

Both codes signal authentication or permission-related issues.