URL Checker

The URL Checker plugin periodically validates the values of URL fields to find those that are bad or are likely to be bad, which helps keep a resource collection up-to-date and useful. The plugin also provides a streamlined interface to view the bad URLs it finds, allowing collection administrators to quickly sort the results, edit the resource associated with a bad URL, hide the resource associated with a bad URL from the public, recheck bad URLs, or even search for a bad URL in Google to find an alternative.

Caveats

The URL Checker plugin doesn't display invalid URLs until they have failed validation at least four times, and each URL is validated once per day at maximum. Thus, it may take a few days for any bad URLs to show up in the results, especially for large resource collections or those with many background tasks running.