Soft 404 | Extended Status Codes (7xx-9xx) | Forum

Some websites report a "Not found" error by returning a standard web page with a "200 OK" response code; this is called a soft 404 or a 704 error. Soft 404s are problematic for automated methods of discovering whether a link is broken.

Soft 404s can occur as a result of configuration errors when using certain HTTP server software.

Example with the Apache software:

is not correct. It generates a 302 redirection to the help.html page showing a "200 OK" response. This is a 704 error or a soft 404.

is correct. It shows the same help.html page with a "404 Not found" response.

Some proxy servers generate a 404 error when the remote host is not present, rather than returning the correct 500-range code when errors such as hostname resolution failures or refused TCP connections prevent the proxy server from satisfying the request. This can confuse programs that expect and act on specific responses, as they can no longer easily distinguish between an absent web server and a missing web page on a web server that is present.

200ok.eu has developed smart algorithms that detect most soft 404 errors. These errors are named 704 errors in our reports.

Credits : derived from the Wikipedia article about "False 404 errors", text available under the Creative Commons Attribution-ShareAlike License.