PURL Enhancement and Stabilization

Since March 1998, the U.S. Government Printing Office (GPO) has used persistent uniform resource locators (PURLs) to provide libraries and other parties stable URLs to online Federal information. GPO's PURL implementation is utilized by Federal depository libraries, Federal agencies, and others to provide persistent links to Federal resources.

In August 2009, GPO's PURL server experienced a significant hardware failure and was unavailable for an extended period. When this happened, all PURL links became inaccessible. The PURL system is a critical tool of the Federal Depository Library Program that fulfills its mission of providing permanent public access to Federal information resources. As a result of the outage, GPO took steps to ensure high availability and redundancy of the PURL application.

Rearchitecture of PURL Software and Hardware

In order to ensure high availability and redundancy, GPO migrated from the original OCLC PURL Resolver Software to the PURLZ Resolver Software, which is a re-architecture of the original OCLC PURL Resolver Software. Included with the migration is the implementation of an improved hosting solution that provides higher availability for the PURL application. Previously, (ro)bot traffic severely hindered the performance of the PURL application and prevented GPO staff from being able to access the system and add/modify PURLs. Under the new hosting solution, the public's and GPO's access is ensured, while still allowing access to traffic, which mostly consisted of link validators.

New PURL Web Address

A new URL of purl.fdlp.gov has been established due to the sunsetting of GPO Access. This new URL ties PURLs to the Federal Depository Library Program. As a result:

  • All new PURLs will use the purl.fdlp.gov address.
  • Direct requests to purl.fdlp.gov will go to a splash page. The domain is used to resolve to Federal resources.
  • All of the 125,000 PURLs that were created using the original OCLC PURL Resolver Software will continue to resolve. No changes will need to be made (at this time) to the existing records that have been made by Federal depository libraries or GPO.

Automated and Enhanced PURL Referral Reporting

As a follow-up from the November 2009 modification of the PURL referral definition and reporting system, an automated PURL referral reporting system was launched on December 1, 2010 that allows Federal depository libraries to view their institution's referrals by individual hostnames and/or IP addresses. The tool also provides a listing of the top fifty (50) referred PURL resources per hostname and/or IP address with:

  • The PURL path.
  • The full path of the target URL for each PURL.
  • The total requests for that individual PURL.
  • A search link utilizing the CGP to view cataloging records for the individual PURL.

GPO still releases monthly PURL referral reports; however, these reports include aggregate totals only. Referrals totals strip out bot traffic and focuses on patron requests.

The PURL Referral Reporting Tool is locked down to Federal depository libraries only. Data is current as of the previous day. Historical data is available for twelve months. Tool functionality may be expanded in the future to include greater historical data retention and additional functionality based on funding and community feedback.

Application Monitoring

The PURL application features high availability and failover services. Traffic routing has been optimized to permit PURL resolution as well as search engines and link checkers.

Learn how Federal depository libraries can utilize PURLs at their institution, more about how PURLs operate, and information on the PURL referral reporting tool, by reading Linking to Federal Resources Using Persistent Uniform Resource Locators (PURLs).

News & Events

July 30, 2020
The U.S. Government Publishing Office (GPO) will freeze the Federal Depository Library Directory (FDLD) so that no changes can be... Read More ...
July 30, 2020
Every Federal depository library may now order up to seven FDLP face masks for their depository staff. If your library has already... Read More ...
July 29, 2020
The U.S. Government Publishing Office (GPO) welcomes Lake Pleasant Public Library, which is located amongst the Adirondack Mountains, as a new... Read More ...
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Welcome to the FDLP!

national collection

GPO welcomes Lake Pleasant Public Library, which is located amongst the Adirondack Mountains, as a new member of the FDLP. Senator Kirsten Gillibrand (D-NY) designated the library and it is the only depository library in Hamilton County in northern NY.

national collection

At Forsyth County Public Library in Winston-Salem, N.C., the Government documents staff are wearing their FDLP masks as they help the public with their Government information needs.


Library Call to Action

PPC Cataloging Manual

The 4th edition of the NACO Participants’ Manual has just been published by the Program for Cooperative Cataloging, and GPO is mentioned in the first sentence: “The Name Authority Cooperative Project (NACO) was established in 1977 as a result of an agreement between the Library of Congress (LC) and the U.S. Government Printing Office to use and maintain a common authority file…” 

Celebrate Constitution Day!!


Celebrate Constitution Day with us!

FDLD and Salesforce

No changes can be made to the Federal Depository Library Directory (FDLD) from Friday, July 31 - Monday, August 10 to ensure that the correct data is migrated to the new Salesforce platform for askGPO.

For Your Library


Prepare your library for reopening with FDLP face masks and social distancing signage.


Access resources for patrons and administrative information for library staff, as well as infographics and images for your library website.

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