HTTP 4xx
404 Not Found
The server could not find the requested resource. The URL may be wrong or the resource may have been removed.
What causes it
- A mistyped or outdated URL, a deleted page, or a broken internal link.
How to fix it
Verify the URL, add a redirect from the old path if the page moved, and fix broken links. A sudden spike in 404s often means a deploy removed a route.
Example response
A typical raw HTTP response a client receives for a 404, with the headers this code is defined around.
HTTP/1.1 404 Not Found
Content-Type: text/html; charset=utf-8Related codes
400Common
Bad RequestThe server could not understand the request, usually because it was malformed.401Common
UnauthorizedAuthentication is required and has failed or not been provided.403Common
ForbiddenThe server understood the request but refuses to authorize it. Unlike 401, authenticating will not help.405
Method Not AllowedThe HTTP method is not supported for this resource, for example a POST to a read-only endpoint.408
Request TimeoutThe server timed out waiting for the client to finish the request.410
GoneThe resource was intentionally removed and will not come back. A stronger, permanent signal than 404.Know before your visitors do.
Sentinel checks your site around the clock from multiple regions and alerts you the moment it starts returning a 4xx error, so you can fix it before it costs you.