Online Public Access Catalog: Definition & Usage

Instructor: Kristen Goode

Kristen has been an educator for 25+ years - as a classroom teacher, a school administrator, and a university instructor. She holds a doctorate in Education Leadership.

An OPAC, or online public access catalog, makes accessing books and other library-related resources easier on users. In this lesson, we will explore a definition and examples of an OPAC as well as the advantages and disadvantages of such a system.

Finding Resources

James is a college student preparing to write a paper for his Biology class. He is in need of several different sources of information and will soon be visiting the college library to find them.

James has a timeline, however, and needs to locate his information quickly. He plans to use the library's online public access catalog to help him narrow his search and locate the sources that will be of most benefit to him as he begins the process of drafting his paper.

Online Public Access Catalogs

An online public access catalog, also known as OPAC, is an online database of all the resources and materials held by a particular library. It is a card catalog, of sorts, that is accessed via computer or other electronic device.

Online public access catalogs could potentially replace the old fashioned card catalog as a means of helping library visitors locate the resources they seek. Users are able to search the database electronically, which can provide them with a quicker and more thorough means of locating necessary information, resources, books, literature, or other materials.

One of the unique aspects of an online public access catalog is that it is user-friendly and accessible by all parties. That means that anybody, regardless of their age, status, or even their level of knowledge about computers, is able to use the system.

If help is needed in a search, the system itself is designed to offer that assistance by use of various prompts, suggestions, help topics, FAQs, and even error messages when needed. Search results are displayed in a format that is easy to read and understand.

The History of OPACs

Online catalogs first became an item in the 1960s, but the first notable and large scale catalogs were not developed until the 1970s (specifically at Ohio State University in 1975 and Dallas Public Library in 1978).

In the 1980s, more and more online catalogs were developed with the introduction of the first commercial systems. After that, however, interest waned, and popularity of the online public access catalog all but disappeared during the 1990s.

Keep in mind that this was all prior to widespread use of the Internet and any of the search engines we have available to us today. New systems and new technologies have put a recent spotlight back on OPAC development with online catalogs now being offered at most libraries across the country.

With so many sources in a library, an online catalog helps keep things organized and findable.

Since the development of the first two notable online catalogs, both have been updated to utilize and include recent technologies and current search protocols. Today, many colleges and universities offer some sort of online public access catalog to help their students gain access to the materials housed in their libraries. Most public libraries have also developed their own versions of an OPAC, making information readily available to library visitors.


To use an OPAC, a library patron or college/university student simply has to access the library link online and then click into the OPAC. Most systems do require an account that will ask for login and password information.

Once logged in, a wealth of information about the library and its contents are made available via searches in many forms. Searches can be done by title, author, date, or even subject. Results offer a link for quick electronic access or by make it clear where each item is physically located.

The OPAC seeks to replace the old fashioned card catalog.
card catalog

Advantages and Disadvantages

The advantages of an OPAC are pretty straightforward:

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