404 Not Found
What is a 404 Not Found HTTP response?
A 404 response is suitable for when a resource was unable to be found at the requested URL.
If a server administrator knows that a resource will no longer be available on a permanent basis then a 410 Gone status code may be preferable.
What type of HTTP status is a 404?
A 404 is in the 4xx class of status codes which are client error based.
There are just less than 30 other status codes in the 4xx class.
Example 404 response
Does a 404 affect SEO?
Yes a 404 can impact SEO. Generally speaking websites should avoid internally linking to 404 pages.
301 redirects may be preferable in some circumstances.
How to set a set a 404
If you are using a CMS such as WordPress, usually deleting a page will set it to be a 404 automatically.
If you need to set a 404 manually there are various methods, depending on what type of CMS and/or Server you are running.
Custom 404 error pages
Because 404 pages are often seen by visitors it is a good idea to have a custom or ‘friendly’ 404 page.
A simple message with a search box and link to the homepage is a lot better for users than a default server error page.
The 404 (Not Found) status code indicates that the origin server did not find a current representation for the target resource or is not willing to disclose that one exists. A 404 status code does not indicate whether this lack of representation is temporary or permanent; the 410 (Gone) status code is preferred over 404 if the origin server knows, presumably through some configurable means, that the condition is likely to be permanent. A 404 response is cacheable by default; i.e., unless otherwise indicated by the method definition or explicit cache controls (see Section 4.2.2 of [RFC7234]).
Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content
Content last checked for accuracy and updated: 1st August 2020, by Colin McDermott