File created in the LEN Exchange Format (LEN), a format used for exchanging swimming data (also referred to as the "Lenex" format); contains information about swimming events that allows record keeping and communication between race organizers, swimming clubs, and associations; most often used for exchanging data for European swimming competitions.

LEF files are commonly packaged into .LXF files, which store the LEF XML data in a .ZIP format. The LXF file format is typically used for data exchange rather than the LEF format because of its smaller file size.