What is a 4xx Error? A Guide to 4xx HTTP Status Codes

HTTP status codes are three-digit numbers returned by servers when a client (like a web browser or search engine bot) requests a resource, such as a webpage or file. These status codes communicate information about the request and response between the client and server.

One category of HTTP status codes is the 4xx status codes. These codes indicate that the client's request was invalid or could not be fulfilled by the server, usually due to a client-side error. Here is a guide to some of the most common 4xx status codes:

400 Bad Request: This code indicates that the server could not understand the client's request. This could be due to malformed syntax, missing or incorrect parameters, or a request that is too large for the server to handle.

401 Unauthorized: This code indicates that the client needs to authenticate itself in order to access the requested resource. This could be due to missing or invalid credentials (like a username and password), or the resource requiring authorization that the client does not have.

403 Forbidden: This code indicates that the server understood the request, but is refusing to fulfill it. This could be due to the client not having permission to access the resource, or the resource being unavailable.

404 Not Found: This code indicates that the server could not find the requested resource. This could be due to a typo in the URL, the resource no longer existing, or the server not having permission to access the resource.

408 Request Timeout: This code indicates that the client did not send a complete request to the server within the time allowed by the server.

There are other 4xx status codes as well, but these are some of the most common ones that you may encounter when browsing the web or working with web applications.