tracev3

The binary file format macOS uses to store Unified Log entries: a header, catalogs and LZ4-compressed chunksets of log entries.

A .tracev3 file is where logd writes Unified Logging entries. It is a sequence of chunks, each with a 16-byte preamble: a header (tag 0x1000) with the boot UUID, build and hardware model; catalogs (0x600b) listing processes and subsystems; and chunksets (0x600d), compressed blocks containing firehose entries, oversize strings and statedumps.

The files live in Persist, Special, Signpost and HighVolume under /private/var/db/diagnostics. See the tracev3 format explained.