6 most common HTTP error codes

HTTP error codes messages can be annoying, but they must be read carefully! They provide valuable clues to know the type of issue you are facing. 

HTTP status codes are essential elements of the Hypertext Transfer Protocol (HTTP) that provide information about the outcome of a client’s request to a server. These three-digit codes serve as a standardized communication method between web browsers and servers, indicating the success, failure, or specific conditions of the request.

These are the 6 most common HTTP error codes you can find!

Error 401, “Unauthorized”

HTTP error 401 expresses the server got an unauthenticated request. The requested resource couldn’t be loaded due to invalid credentials or lack of them.

Causes can vary. A plugin bug or incompatibility, an outdated link, an incorrect URL, or outdated browser cache and cookies could be blocking a successful authorization to access the resource. And without it, the server will discard the request.

Error 404, “Not found”

The 404 HTTP error code says the server couldn’t find the requested resource. The code doesn’t provide further details about the resource, like if it’s temporarily gone or permanently. 

There are different reasons for a resource not to be found. It’s a web page that doesn’t exist anymore due to prior deletion. There’s a broken link or a link incorrectly placed that’s not directing as it must. Actually, dead or broken links frequently cause this error. An exhaustive checking will be required to find and fix the problem.

Error 410, “Gone”

This HTTP error 410 points out the requested resource is permanently gone. The webpage is not available, and there’s no other URL or redirection way to reach it. Causes are different, but broken external links are commonly the guilty ones. Adding links that drive users to other sites is useful to support or go deeper into a topic. But since they are external, they can be deleted anytime, and their link will send users to a gone resource. When search engines read this error, they de-index the page. If the resource truly exists, but there’s a mistake, not fixing it fast will affect your traffic.

Error 500, “Internal server error”

HTTP error 500 reports the server is experiencing a problem. Due to this, the request can’t be completed.

Many different problems can cause internal server errors. Third-party plugins conflicts, scripting language bugs, lack of connection with the database, you name it! Downtime is by itself a big issue that must be diagnosed and fixed fast! Besides, since all these issues can be prevented through regular maintenance, search engines read this error 500 as a badly maintained site. 

Error 502, “Bad gateway”

Different scenarios can cause the error 502 message to be displayed. For example, a server got a not valid answer from another server. Also, if answering a request takes more time than usual for the server, it will cancel it, and as a result, the communication with the database will be broken. Therefore, problems between servers totally deserve attention and to be fixed.

New websites can experience error 502 when their DNS data haven’t been completely propagated. Just in this case, the solution for the error is simply to wait. The propagation has to be completed, and the problem will be gone.

Error 503, “Service unavailable”

HTTP error 503 says that the server is down. The code doesn’t explain the cause, type of failure, or temporary or permanent. It just tells users, other machines, and search engines to try later. In any case, this must be checked as soon as possible not to lose traffic.

Causes can be different, regular maintenance, normal initializing process, an overload, etc.


HTTP error codes are useful for machines to inform the status of HTTP requests. Good knowledge about what these codes mean will make faster your diagnose and troubleshooting process.

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