W3 Catalog was a very early web search engine

Web search engine

A web search engine is designed to search for information on the World Wide Web and FTP servers. The search results are generally presented in a list of results often referred to as SERPS, or "search engine results pages". The information may consist of web pages, images, information and other...

, first released on September 2, 1993 by developer Oscar Nierstrasz

Oscar Nierstrasz

Oscar Marius Nierstrasz, born , is a Professor at the Computer Science Institute at the University of Berne. He is active in the field of...

 at the University of Geneva

University of Geneva

The University of Geneva is a public research university located in Geneva, Switzerland.It was founded in 1559 by John Calvin, as a theological seminary and law school. It remained focused on theology until the 17th century, when it became a center for Enlightenment scholarship. In 1873, it...

.

Unlike later search engines, like Aliweb

Aliweb

ALIWEB is considered the first Web search engine, as its predecessors were either built with different purposes or were literally just indexers ....

, which attempt to index the web by crawling over the accessible content of web sites, W3 Catalog exploited the fact that many high-quality, manually maintained lists of web resources were already available. W3 Catalog simply mirrored these pages, reformatted the contents into individual entries, and provided a Perl

Perl

Perl is a high-level, general-purpose, interpreted, dynamic programming language. Perl was originally developed by Larry Wall in 1987 as a general-purpose Unix scripting language to make report processing easier. Since then, it has undergone many changes and revisions and become widely popular...

-based front-end to enable dynamic querying.

At the time, CGI

Common Gateway Interface

The Common Gateway Interface is a standard method for web servers software to delegate the generation of web pages to executable files...

 did not yet exist, so W3 Catalog was implemented as an extension to Tony Sander's Plexus web server, implemented in Perl

Perl

Perl is a high-level, general-purpose, interpreted, dynamic programming language. Perl was originally developed by Larry Wall in 1987 as a general-purpose Unix scripting language to make report processing easier. Since then, it has undergone many changes and revisions and become widely popular...

.

W3 Catalog was retired on December 8 1996.