Error 401 - how to fix the HTTP Error Unauthorized?

In successful communication between client and server, status messages remain invisible. However, if an HTTP error occurs, it is displayed to the visitor to provide a hint for solving the problem. Many of them, such as the Error 522 "Connection timed out", are not clear. In contrast, the Error 401 "Unauthorized" can be quickly and clearly identified. This makes it a problem that can be easily resolved by an administrator if the HTTP error occurs unexpectedly and not due to an intended access restriction.

What is an HTTP error like Error 401?

When a client, such as a browser, requests a webpage from a server, both parties exchange status messages that describe the state of the connection and any issues. These messages consist of numerical codes with a brief description and can be classified into five different categories:

• HTTP Code 100 - 199 provides detailed information about a connection
• HTTP Code 200 - 299 confirms the successful transmission of information
• HTTP Code 300 - 399 indicates a redirection by the server
• HTTP Error 400 - 499 describes a problem caused by the client
• HTTP Error 500 - 599 means the server cannot process the request

This classification allows the HTTP protocol to be expanded with new codes in later versions and enables a quick, intuitive assessment of the connection status. Error 401 "Unauthorized" corresponds to an HTTP error triggered by the client according to this classification.

What triggers the Error 401 "Unauthorized"?

When Error 401 "Unauthorized" occurs, it specifically means that a client lacks permission to access the corresponding page. Unlike, for example, Error 400 "Bad Request" or 403 "Forbidden", this is not due to a general denial but to a restriction set up by the webmaster, requiring authentication such as a password prompt. However, in practice, the error can result from either inadequate identification or communication issues. Possible causes include:

• Incorrect combination of username and password
• Outdated and invalid data in the cache or cookies of a browser
• Incorrect redirection by a router, server, or other node
• Web server configuration inheriting settings to the subfolder
• Unsupported special characters in the login
• Authentication is invalid or expired

In most cases, a 401 "Unauthorized" error occurs due to faulty authentication, which the server rejects for this specific reason.

How to fix a 401 error?

Unlike other user authentication methods within Content Management Systems (CMS), the 401 "Unauthorized" error operates as a general HTTP error not at the software level, but is based on immediate access control by the web server. Specifically, the Apache 2 web server offers the ability to prompt for passwords using .htaccess files, providing a simple and functional method to restrict access to websites or parts of them for public access. It should be noted that entering the login incorrectly once or multiple times may result in it being stored in cookies or the cache. Upon revisiting, the user may not have the opportunity to correct the data because the browser does not differentiate between a 401 "Unauthorized" error and a regular webpage, storing it as successful access. As a client, the only way to bypass the HTTP error is to enter valid data. If an unwanted prompt occurs, the administrator must locate its source. This usually results from either a manually created .htaccess file or settings in an administration tool like Plesk, Webmin, or DirectAdmin.

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