The U.S. Government Publishing Office (GPO) operates the Federal Depository Library Program (FDLP), which was established by Congress to ensure that the American public has access to its Government’s information. As part of its mission, the FDLP acquires and distributes federal information to the American public both online and through Federal Depository Libraries located in the 50 states, the District of Columbia, and U.S. territories.

As part of the online dissemination of federal information, the FDLP uses persistent uniform resource locators (PURLs) to provide stable URLs to online federal information. When a user clicks on a PURL, the request is routed to the federal publication. As federal agencies redesign and remove information from their sites, GPO staff reroute PURL entries to the appropriate location.