4xx Client errors
404 Not Found
Nothing exists at this address.
Common causes
- A mistyped or old link.
- A page that was deleted or moved without a redirect.
- A deployment that's missing files or routes.
How to fix it
- Redirect old URLs to their new location with a 301.
- Fix broken internal links.
- If a whole site returns 404 after a deploy, check the build output and routing.
Find out the moment your site returns 404
Spot Downtime monitors count this as down and alert you, since visitors see an error. (The public “Is it down?” checker treats 4xx answers from big sites as online, because many refuse automated requests.)