HTTP status codes. Error 500, error 502 and more.

Any now and then, when we are browsing the internet, we get one of those – error 500 or error 404. What does this number mean? How many other numbers are there? In this article you will see the different categories of HTTP status codes, what do they say and some examples.

HTTP status codes

1?? Informational

The informational HTTP status codes show you that the request is received without problems, but you need to wait until it gets processed.
100 Continue. The server is not ready with your request. It still needs to work on it. It may be due to a large request that needs more time.
103 Early hints. The request might be too large, but you are getting some information before the final complete response.

2?? Success

Computers can show not just errors but also successes. These next codes show when a request is completed correctly.
200 OK. This message indicates a completed request. The request could be GET, HEAD, POST or TRACE.
201 Created. The request has led to the successful creation of a new resource (POST or PUT).
204 No content. The server, after processing properly your request, tells you that it won’t return any content.

3?? Redirection

If you have worked in SEO, you probably already know these redirects. They help you organize websites, especially after internal changes.
301 Moved Permanently. If somebody moves an article from one category to another, its URL will change too. You need to point the old URL to the new one.
302 Found or Moved temporarily.
The “moved temporary” has never been a popular and useful redirect. It was used like the 301, but if you move an item for just a short time.
304 Not modified. Basically what this redirect tells us is that the file we requested, has no new modification from the last time we requested it. Your computer should have it in the cache.

4?? Client Error

In a client-server model, there are two sides, the client for easy use and server which answers queries from the different users. The 4?? errors are mostly due to a problem with the client or just answer of a request.
400 error, bad request. The server says that it will not continue with the request, because of an inappropriate request (probably a syntaxes error).
401 Unauthorized. This is when the person who wants to access has failed with the authentication.
403 Forbidden. Similar to 401 error, but here there is no fail, just the user has no access to that place whatsoever.
404 Not found. The most common error, when we are searching for an old article. 404 Not found will appear when the there is no redirect and the page is just gone.
409 Conflict. The current state of the resource has a conflict that doesn’t permit the request.

5?? Server Error

Here are a few status codes that you might see often if you work with servers. This category is for the server part of the connection.
500 error – the most generic error possible. It doesn’t tell you anything more than the error is in the server.
502 error – bad gateway. The server was doing a job as a proxy or a gateway and got an invalid response from another upstream server.
503 Service unavailable. This you can see when the server gets too many task and overload or is down due to maintenance.
504 Gateway Timeout. The server, who was performing as a proxy or a gateway, didn’t receive a response in time from the upstream server. There could be a problem with the next server on the network.

Conclusion about HTTP status codes

There are even more HTTP status codes out there, but these are the most common. Now that you know what they mean, you can understand better the network and know where to search for the problem. Hope it was interesting for you, if you want to know about another code that is not in our list, put it in the comments.

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