There are a few copies of the Catechism of the Catholic Church online, and they all have a very simple search interface. While this might be helpful when looking up words like "Incarnation" or "Purgatory", these search interfaces are not very robust. What's more, they don't enable readers to identify paragraphs of the Catechism which make reference to a particular passage of Scripture.
Enter the Catechism Search Tool made available at The Cross Reference. This utility, approved for use by the USCCB Subcommittee on the Catechism, enables Catholics (and others) to search and view the entire text of the Catechism -- paragraphs and footnotes -- in a variety of ways:
- By reference to Scripture verses
- By text (exact phrase, all words, any words, partial words, even support for regular expressions)
- By paragraph number
- By Catechism section
The full content of the Catechism is made available, including the cross-references between paragraphs.
In addition to the Catechism Search Tool, there is a similarly-designed search tool for the Compendium to the Catechism. Also available is a Lectionary Search Tool, allowing you to find out the readings for a given liturgical day, or find the liturgical days which include a given Scripture passage. This tool provides paragraphs numbers from the Catechism whenever a Scripture passage is found in the Catechism. Last but not least is a Magisterium Search Tool which provides robust text searching for over 100 documents of the Magisterium (going back nearly 150 years).
These search tools are all written in Perl.