404
/fɔːr oʊ fɔːr/ · Noun · Adjective · Slang & Abbreviations · Origin: 1992
Definitions
404 is the HTTP status code that means Not Found, returned by a web server when the requested resource does not exist at the specified URL. It is one of the most recognizable error codes on the internet, often encountered when a page has been deleted, a link is broken, or a URL is mistyped. The 404 status belongs to the 4xx family of client error responses defined in the HTTP specification (RFC 7231). Many websites customize their 404 pages with helpful navigation, search bars, or humorous content to improve the user experience when visitors land on missing pages. In web development, monitoring 404 errors helps identify broken links and content gaps. The term has entered mainstream culture as shorthand for something that cannot be found or does not exist.
In plain English: The famous error code meaning 'this page doesn't exist' — also used as slang for anything that's missing or can't be found.
Used as slang in everyday conversation to mean clueless, absent, or unable to be found. '404' has become a general metaphor for anything that's missing, broken, or unresponsive — including people.
Example: 'I asked the new PM about the roadmap and got a total 404. I don't think they've read the brief.'
Source: slang
Etymology
- 1989
- Tim Berners-Lee proposes HTTP at CERN. Error codes are part of the protocol design from the start.
- 1992
- HTTP/1.0 specification formalizes status code 404 to indicate a resource not found on the server.
- Late 1990s
- Custom 404 pages become a creative outlet for web designers. The code enters popular culture.
- 2010s
- '404' becomes everyday shorthand for anything missing or unfound, well beyond its technical origin.
Origin Story
Room 404 at CERN — or was it?
The legend goes that Room 404 at CERN housed the first web server, and when a requested page wasn't found, the error was 'Room 404: File Not Found.' It's a great story, and it's almost certainly false. CERN has no Room 404 in the relevant building.
The truth is more mundane: HTTP status codes were defined by Tim Berners-Lee and his team in the early 1990s. The 4xx range was designated for client errors (you asked for something wrong), and 404 was simply the code for 'Not Found.' There's no room, no hallway, no dramatic origin.
But the urban legend persists because it's more interesting than the truth, and because 404 has transcended its technical meaning. It's become a cultural shorthand: '404: motivation not found,' '404: sense of humor missing.' Few error codes have become metaphors for absence itself.
Coined by: Tim Berners-Lee / HTTP Working Group
Context: CERN, early 1990s
Fun fact: The Room 404 origin story has been debunked multiple times, but it keeps resurfacing — perhaps because people prefer a good story to a spec document.