CRAM
From Just Solve the File Format Problem
CRAM is a binary format for aligned DNA sequencing. The .cram files are the CRAM data, while .crai is an associated index file.
Identification
Files start with the four bytes spelling CRAM (hex 43 52 41 4d) followed by the major and minor version numbers as unsigned bytes, then a 20 byte file ID (name or SHA1 checksum).
