The ECO extension is given to files by a personal information management software called Ecco Pro. ECO files were used to store a user-created database in the program. The structure of such a file was based on a table similar to that in typical databases. Data in ECO files could be filtered by the program and displayed based on the criteria set by the user. Schedules, contact books, addresses, etc. could be stored in the ECO databases.

Currently, ECO files like the Ecco Pro program are rare and are considered obsolete.