docs/Peer-ID-and-User-Agent.md
Transmission's peer-ids follow Azureus' style with code TR. Peer-id prefix is -TR????-, where ???? are four bytes encoding the client's version. Client version encoding changed over the client's history.
Starting from version 3.00, peer-ids are formatted -TRXYZR- where X, Y, Z are base62 major, minor, patch version numbers, and R is one of 0 (stable release), B (beta release), or Z (dev build). For example:
-TR40aZ- — 4.0.36 Dev-TR400B- — 4.0.0 Beta-TR4A00- — 4.11.0The suffix scheme was changed after 3.00 for consistency with other clients.
From version 0.80 up to 3.00, Transmission's peer-ids were formatted -TRXYYR-, where X was one base10 digit for the major version and YY were two base10 digits for the minor version. R was a suffix denoting a stable release (0), nightly build (Z), or prerelease beta (X). For example:
-TR133Z- — Nightly build between 1.33 and 1.34-TR133X- — 1.34 Beta-TR1330- — 1.33Rationale at the time: this differentiates between official and unofficial releases in a way which is easy for trackers to detect with simple string comparison. An official release (-TR1330-) is lexicographically smaller than its post-release unsupported versions (-TR133Z- and -TR133X-), which in turn are lexicographically smaller than the next official release (-TR1340-).
Before 0.80, Transmission used two base10 digits for the major version and two base10 digits for the minor version. For example:
-TR0072- — 0.72-TR0006- — 0.6Its User-Agent header follows a similar format, plus the VCS revision in parentheses: