| 1 | Cannot resolve name | The URL contained a host DNS name that could not be resolved. |
| 2 | Socket failed | Unable to get a local socket to begin the connection process to contact the HTTP server responsible for the resource identified by the URL. |
| 3 | Connection failed | Unable to connect to the HTTP server responsible for the resource identified by the URL. |
| 4 | Timed out | Communication with HTTP server responsible for the resource identified by the URL timed out. |
| 5 | Invalid response | The HTTP server responsible for the resource identified by the URL returned an invalid of NULL status code in the HTTP response. |
| 6 | Invalid redirect | The HTTP server returned an invalid redirect URL. |
| 10 | Too many redirects | During validation, multiple redirects occurred in such a fashion as to produce a loop or the maximum number of redirects allowed was exceeded. In either case, the actual item requested was never successfully retrieved. |
| 20 | User not authorized | The user requesting validation is not authorized to perform validation on (not a maintainer of) this PURL. |
| 21 | No Results | The user requested results for a PURL that does not exist in the results database. |
| 22 | Not A PURL | The user submitted an entry that was not found in the PURL database. |
| 23 | Partial Redirect | The user submitted an entry that is a partial redirect. |
| 24 | Disallowed via /robots.txt | The user submitted an entry that is disallowed because of an entry in /robots.txt.. |