404

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/fɔːr ˈoʊ ˈfɔːr/
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A numeric code used by the Hypertext Transfer Protocol to signal that a requested web resource is not available.

Examples

  • Developers should log every 404 to monitor missing resources.
  • Our analytics show many users encounter 404 after clicking broken links.
  • Search engines may lower rankings if a site has many 404 responses.
  • A custom 404 page can guide visitors back to useful content.
  • The browser displayed 404 when the page was missing.

Similar words

resource not found
Not Found
missing page error
404 error
HTTP Not Found
client error

Meanings

Usage

Use 404 when a web page cannot be found; avoid using it for server errors or in non‑web contexts.

Common mistakes

Confusing 404 with server errors, such as using it for a broken device, leads to misunderstanding.

Etymology

From the Hypertext Transfer Protocol, where status code 404 was assigned to indicate a “Not Found” condition.

FAQ

What does 404 mean?

404 is the HTTP status code that indicates a requested web page could not be found.

When should I use 404?

Use 404 whenever a URL points to a missing or removed resource on a web server.

Is 404 a client or server error?

404 is classified as a client‑side error because the request was understood but the resource was absent.

How does 404 differ from 500?

404 signals a missing page (client error), while 500 indicates an internal server error.

Can a 404 page be customized?

Yes, web developers often design custom 404 pages to help users navigate back to useful content.

Why do browsers show a 404 page?

Browsers display a 404 page when the server returns that status, informing the user that the page does not exist.

How can I fix a 404 error on my site?

Fix a 404 by correcting broken links, restoring moved pages, or updating references to the correct URLs.

Does 404 affect SEO?

Frequent 404 responses can hurt SEO because search engines may view the site as poorly maintained.

Is 404 used outside of web contexts?

The term 404 is primarily a web‑specific code, though it is sometimes used metaphorically to mean “not found.”

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