LERC (Limited Error Raster Compression), also written Lerc, is a format for compressed raster image data. It was developed by Esri.
There are two major versions, known as "Lerc1" and "Lerc2".
The OptimizeRasters project suggests that the usual filename extension is .lrc.
Lerc2: Files start with ASCII "
Lerc2 " (note trailing space).
Lerc1: More research needed. Some files start with "
See also Meta Raster Format#Software.