111 Revalidation Failed
When a cache cannot reach the origin server to revalidate a stale response, the 111 Revalidation Failed warning code is attached to the Warning header. The code indicates the response is stale and the revalidation attempt did not succeed.
Note
The warning code 111 Revalidation Failed and the Warning header have been obsoleted.
Example
Warning: 111 www.example.re "Revalidation Failed"
See also
Last updated: April 4, 2026