What is Z39.50?

Z39.50 is a standard protocol for accessing databases over the Internet. The term “Z39.50” refers to the International Standard, ISO 23950: "Information Retrieval (Z39.50): Application Service Definition and Protocol Specification," and to ANSI/NISO Z39.50. With the rapid growth and development of search engines and searching techniques, the Z39.50 protocol can provide a standard interface gateway to multiple databases, allowing for simultaneous searching against diverse products. Encyclopædia Britannica Online's encyclopedic database is accessible using the Z39.50 protocol.



How do I use Z39.50?

The Encyclopædia Britannica Online database can be accessed using specific Z39.50 client software.

The commercial applications have the advantage of support and installation instructions. For those who have limited resources, here is a freeware client:


There is also a Unix client version available for Solaris 2.x, 7 and 8. You can get it at the link below, along with extensive documentation on installation.




How to search with Z39.50?

Searches using Z39.50 support the following Boolean operators:

     AND (to narrow the search)

     OR    (to broaden the search)

     AND-NOT (to remove irrelevant components of a search)

All searching is case insensitive. Wildcard searching is not supported.

While it is beyond the scope of this page to document the installation and configuration of each of these software packages, especially since each package has its own installation instructions, the connection specifics must be given.


For the Encyclopædia Britannica Online encyclopedic database, the connection parameters are as follows:

  Server address: z3950.eb.com

  Server Port: 210

  Database Name: XXDEFAULT

  Preferred Message Size: 16kB

  Record Syntaxes: USMARC SUTRS

  Search Attributes:

   "Use" attribute 4 - title, can be used on its own or with "structure" attribute "word" (2) or "wordlist" (6)

   "Use" attribute 12 -  local number - can be used on its own or with "relation" attribute "equal" (3)

If you experience any difficulties please contact Encyclopædia Britannica Customer Support at 800-621-3900. More information on Z39.50 can be found at the following addresses: