CRAM

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  (hex  ) followed by the major and minor version numbers as unsigned bytes, then a 20 byte file ID (name or SHA1 checksum).

Spec

 * CRAM v2.1 spec
 * CRAM v3 spec

Links

 * CRAM Toolkit