Ed Summers, librarian, metadata expert, teacher, and computational expert, delivers an insighful lesson on the Persistent Uniform Resource Locator. PURLs were developed to make URLs more resilient and persistent over time. You could put a PURL into a catalog record and if the URL it pointed to needed to change you changed the redirect on the PURL server, and all the places that pointed to the PURL didn’t need to change. It was a beautifully simple idea, and has influenced other approaches like DOI and Handle. But this simplicity depends on a commitment to keeping the PURL up to date.