• Last Updated: August 18, 2021
  • Published: January 27, 2009

Use any Z39.50 client to automatically retrieve records from the Catalog of U.S. Government Publications (CGP).

Z39.50 is an American National Standards Institute (ANSI)/ National Information Standards Organization (NISO) communications protocol. It is used to search and retrieve bibliographic records in online databases of library holdings. It also allows you to download bibliographic records in MARC format and load into your library’s bibliographical database at no cost. Records supplied by GPO via Z39.50 are encoded in MARC8. For more information, please see The ANSI/NISO Z39.50 Protocol.

How to Connect

Login Information

Access to the CGP via Z39.50 is limited to Federal depository libraries via username and password.

  • Username: z39

To get your Z39.50 password, use the CGP Lost Password feature. You will receive an email with your internal password and your Z39.50 password.

Connection Settings

Use the following connection settings to access the CGP via Z39.50:

  • Hostname: Z3950.catalog.gpo.gov
  • Port: 9991
  • Database Name: gpo01pub
  • Record Type: USMARC

ILS Configuration

If a Z39.50 client is built into your Integrated Library System (ILS), configure the settings for "Z39.50 gate". You also need to map the “Bib-1” attributes that the CGP supports in your Z39.50 gate for the CGP target. Contact your ILS system staff or vendor for assistance.

Client Software Configuration

If you don’t have a Z39.50 client built into your library system, you will need to download Z39.50 client software. View a list of free and commercial programs. For questions or problems connecting using client software, contact the respective vendor.

Line-Mode Client

The following is an example connection procedure for a line-mode Z39.50 client (e.g., YAZ-client):

Z> authentication z39/password   ---> (hit ‘Enter’)
Authentication set to Open z39/password   ---> (System response)
Z> open tcp:Z3950.catalog.gpo.gov:9991/GPO01PUB   ---> (hit ‘Enter’)
Connecting … OK

Commercial Citation Software

The following is an example connection procedure for commercial citation software (e.g, EndNote, RefWorks).

Download Limit

There is a limit of 10,000 record at a time. If using scripts, please be mindful we have a limit on the number of concurrent uses that can access our Z39.50 at a time, and that aggressive scripts may cause adverse effects to response time, functionality and connectivity which may require the termination the offending session(s).

Z39.50 Attributes

  • A list of GPO’s Z39.50 attributes is available from the CGP.
  • A complete list of “Attribute Set Bib-1” is available from the Library of Congress.