SEGB

SEGB is the binary container format that Biome uses for its stream files, named after its SEGB magic value. Two versions are known. Version 1 has a 56-byte header with the magic at bytes 52 to 55, followed by records that each start with a 32-byte header (length, state, two timestamps, CRC32). Version 2 has a 32-byte header that starts with SEGB and indexes its records through a trailer of 16-byte entries at the end of the file.

Every record has a state: 1 written, 3 deleted, 4 empty. Deleted records can still contain data, so they deserve a look. A CRC32 computed over the payload flags partial or damaged writes. On iOS, v1 is reported for iOS 14 to 16 and v2 from iOS 17; the boundary on macOS is not publicly documented, so tools detect the version from the header.

Offsets and field layouts are in the Biome SEGB file format.