From LDraw.org Wiki
LDR file
LDR icon.png
Filename extension .ldr
Internet media type application/x-ldraw
Developed by James Jessiman
Type of format Document file format
File format infobox

LDR is the default file format used by the LDraw system. It usually will contain a model built from official or unofficial parts.

One or more LDR files can be combined into an MPD file.

Different than models, parts use the DAT file extension instead by convention.

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