Why Is it Called a 404 Error?

(Last Updated On: November 1, 2022)

If you’ve ever tried to do any amount of research on the internet, you’ve encountered the dreaded 404 error. Because when you’re on a time crunch with getting information you need for a project, the internet spontaneously decides every source you need is going to be inaccessible. Now that you’re no longer banging your head against the wall, why is it called a 404 error, though? 

Here’s what ours looks like:

Room 404

There’s a fun conspiracy theory floating around that asserts “Error 404” is actually named after a specific place. The legend tells that when CERN was developing the infrastructure of the internet, they did so on the fourth floor of their office. Our fourth-floor team was tasked with creating a system of data delivery. Allegedly there was a Room 404. The people who worked there were supposed to be tasked with transferring files across the early web–but they had to do so manually. Because all user input is error, it was difficult for them to get files to requesters; they would ask for the wrong file names. 

Thus, “404: file not found” is said to have been born from this team working in Room 404. 

What Does 404 Actually Mean?

404 is an HTTP error, you might recognize it for being at the front of all your URLs. HTTP stands for Hypertext Transfer Protocol. HTTPS is more common at the front of your URLs, but really it’s just a secure version of HTTP. The whole thing is set up to facilitate communications between you and servers. So when you put in a request to go find something online through your internet browser of choice, the HTTP protocol has the server go off and essentially gathers what you need and sends it back as response. 

Of course, when something goes wrong, the server still has to tell you there was an issue so you’re not left hanging. The fact that the server returns an error in the first place also gives you some information. It tells you that the server itself is actually up and running. The problem was on your end–you submitted a request for something that wasn’t there. You can imagine client-server requests like asking a librarian for a book in a giant library. Except instead of saying “can you find me Harry Potter?” you’re asking “can you get me the third book on the fourth shelf, which should be Harry Potter?” When you get a 404, that’s the librarian saying while the shelf and library exist, there either isn’t a book there or there’s a different book there instead. 

The most common cases for a 404 return are when you give a bad URL. That would be like saying “can you get me the third book on the fourth shelf, which should be Parry Hotter?” Alternatively, webpage you’re looking for may have just moved. That would mean Harry Potter is still somewhere in the library–it’s just not where you asked the librarian to look. 

Why 404?

The creation of the 404 error starts with a guy named Tim Berners-Lee, and he talks about how the error was born in a Ted-Talk

Before the 404 error, all links had to be validated to make sure they went somewhere, which meant that any time something on the internet was moved, everything had to be updated. Obviously, this is super inefficient. While easier for users–it meant that everything had to be verified through a centralized authority that could validate everything. Considering the volume of the internet, that’s just not possible. It becomes even less possible when you consider link rot, which is the tendency for links to stop pointing to their intended destinations over time. So the 404 error essentially says “don’t go through the effort of validating every single links, if the link points to something that doesn’t exist, then that’s okay.” 

It’s the internet-equivalent of codifying what “zero” means. 

404 wasn’t an arbitrary designation, and it does actually mean something. The “4” at the beginning of “404” means the error is client-side. That means you submitted a request that led to nowhere. “0” means the client-side error was a general syntax error–like misspelling your URL or requesting one that didn’t exist anymore. The last “4” is even more specific, it means your misspelled request found nothing. 

Speaking of errors, see if you can pick out geographic ones here

About the Author:

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Kyler is a content writer at Sporcle living in Seattle, and is currently studying at the University of Washington School of Law. He's been writing for Sporcle since 2019; sometimes the blog is an excellent platform to answer random personal questions he has about the world. Most of his free time is spent drinking black coffee like water.