Definition
JoinMarket is open-source software for building CoinJoin transactions, with an incentive structure designed to make collaborative privacy practical. It creates a marketplace for CoinJoin liquidity: participants who are willing to wait offer their coins for mixing, and participants who want to mix immediately pay a fee for the privilege. Throughout, private keys never leave the user's wallet, so the system is fully non-custodial.
Makers and takers
JoinMarket runs on an order-book model with two roles. Market makers are patient participants who post standing offers — their fee, how much they will contribute to miner fees, and the denominations they will mix — and earn fees when others join with them. Market takers are time-sensitive participants who pick from those offers and pay to create a CoinJoin on demand. This fee market keeps a pool of liquidity available so a taker can usually mix instantly rather than waiting for enough volunteers to coincide.
Why the marketplace matters
Earlier CoinJoin tools struggled because they needed several users wanting to mix the same amount at the same moment. By paying makers to provide liquidity, JoinMarket decouples the taker's timing from other users' schedules and rewards people for contributing to a larger anonymity set. Coordination has historically happened over messaging transports such as IRC.
JoinMarket represents the decentralized, market-driven branch of Bitcoin CoinJoin, contrasting with coordinator-run equal-output systems like Whirlpool. For the underlying technique, see CoinJoin.
In Simple Terms
JoinMarket is open-source software for building CoinJoin transactions, with an incentive structure designed to make collaborative privacy practical. It creates a marketplace for CoinJoin liquidity:…