The .LXF file format is used by LEGO Digital Designer (LDD), a virtual LEGO building application by the LEGO Group.

These files are saved using the .ZIP compression format and within each .LXF file, there are three files:

- MODEL100.MODEL

A binary LXF scene file

- IMAGE100.PNG

A thumbnail images of the model

- IMAGE100.LXFML

An XML formatted documents which describes the location of the bricks.