Its dictionaries can be consulted free online from any web browser or from LEO's Lion downloadable user interface (GUI), which is free since version 3.0 (released 13 January 2009), to private users only, and no longer sold as shareware.

For any of the eight foreign languages, there's at least one (in the cases of English and French two) qualified employee in charge (whose mother tongue is either German and who has studied the respective other idiom or vice versa).

[1] The English-German dictionary run by Leo since 1995 contains around 800,000 entries and receives an average of 11 million queries per weekday.

At the time of the public launch, the dictionary contained about 140,000 entries and received 77,000 queries on the first day.

The starter database has been provided in collaboration with ABBY Europe GmbH, the producers of the Lingvo dictionary brand.

[10] In 2013, a Polish-German dictionary was started which contains over 74,000 entries by November 2019 and receives almost 80,000 queries every weekday.

[11] The site grew out of a network of FTP software and archived data which was put together by students at Munich University of Technology and Ludwig Maximilian University of Munich even before HTML and HTTP existed.

When the World Wide Web came into common use, HTTP access to the archive was at first added as an alternative to FTP.