Files with the CON extension are associated with a Corel text editor named WordPerfect. CON files contain a set of words and phrases used when creating indexes in documents. The program compares the content of the document with the CON file and if a given phrase or word is found in the text, the index will be inserted with the page number where the text appears.

WordPerfect is a product developed by Corel and is now part of the WordPerfect Office suite.