gammonchainBackgammon you can verify

An open-source online backgammon server where no one, including the server, can predict or steer the dice, and every finished match is a signed record anyone can re-check offline.

Play at gammonchain.com

How the dice work

Self-host it

Dice nobody can predict

Each player commits to a reverse hash chain before play and reveals one link per roll. The server does not have your next link; you do not have the server's seed. Neither side can compute the next roll.

A record that proves itself

Every roll, play and cube decision is hashed into a chain and signed with Ed25519 by the server and by both players. Change one byte and verification fails.

A verifier you run yourself

The same rules engine the server runs replays the whole match. It re-derives the dice, re-validates every play and checks that both named players actually signed.

Ratings, clocks, bots, analysis

Glicko-2 weighted by match length, reserve-plus-delay clocks, three bot levels, a daily puzzle, and analysis priced in match equity at the actual score.

One small process

Node, WebSockets, one SQLite file and gzipped records. One runtime dependency. Measured at 231 MB RSS holding 200 concurrent 9-point matches.

Honest about the limits

The docs state what the design does not defend against, including a server that deliberately leaks its seed to a colluding player.