Why the 404 error ?

Hello everyone, today we're going to look at HTTP errors, you know like when you get a page not found with the 404 error. In reality there are almost a hundred different error codes. Don't worry, it's difficult to know them all by heart, but there are techniques to find out roughly where the error comes from. You are ready, so let's go !

Why did you invent these numbers ?

But then why did we invent these error numbers? The answer is actually quite simple, when a user requests a web page through his browser, the browser will send a request to the server under the world famous HTTP protocol. The server will also respond in HTTP format, and if all goes well will send the requested resource (in our case the web page). But everything gets complicated when there is an error. Knowing that there is an error is good, but knowing where is even better. This is why error numbers were quickly assigned to each different type of error. This is much more practical and saves time for many developers. For example, errors starting with 5 are problems at the server level.

The five categories of error

To simplify the whole thing, and to put some order in all these errors, categories have been created. There are three different categories:
1 - Informations
2 - Success
3 - Redirects
4 - Web client errors
5 - Server errors

So if an error number starts with 4, we know directly that the problem comes from the web client.

Why 404 error ?

But why 404 errors? If you have been following this, you will notice that the first number is a 4 and that the error comes directly from the web client and not from the server. Indeed, the 404 error means that the resource is not found, the server has searched for it on its side but has not found it, so the error comes from the web client which has not provided the right url.

Going further with error 418

The HTTP error 418 has nothing to do with the other errors. Indeed its meaning is "I'm a teapot". It is actually a joke since it first appeared in the famous RFC 2324 on April 1, 1998. The explanations given by the developers are: " There is coffee all over the world. Increasingly, in a world in which computing is ubiquitous, the computists want to make coffee. Coffee brewing is an art, but the distributed intelligence of the web- connected world transcends art. Thus, there is a strong, dark, rich requirement for a protocol designed expressly for the brewing of coffee. Coffee is brewed using coffee pots. Networked coffee pots require a control protocol if they are to be controlled".
In other words, the famous Hyper Text Coffee Pot Control Protocol, or HTCPCP, is intended to send an error back to all those who would like to control a coffee pot remotely, telling them that they have mistakenly addressed themselves to ... a teapot .
This April 1st "joke" had its heyday at the time and is still featured on a number of official links in which its error code has been preserved.
There are still people asking questions about this 418 error, even today!

Specific errors

For those who wish to find a specific error, you can refer to these different tables classified by categories.
Some codes are not yet in use, but are intended for future use. Other codes do not result in any specific display to the user, but are implied (e.g. codes 200 or 304, which are never seen by the client as they concern the majority of successful requests).

All major HTTP errors are represented in these different tables, of the different error types:

Codes beginning with 1 (Informations):

Codes beginning with 2 (Success):

Codes beginning with 3 (Redirects):

Codes beginning with 4 (Web client errors):

Codes beginning with 5 (Server errors):

I hope you have enjoyed this article. If you have any questions, feel free to ask me in the comments.