CoinJoin
wallets · advanced
A collaborative transaction where multiple users combine inputs and outputs to break the link between sender and recipient on-chain.
CoinJoin was first described by Greg Maxwell in 2013. The mechanism is simple: several people contribute inputs to a single transaction and receive same-valued outputs back. From outside, an observer cannot tell which output belongs to which input — they only know the participants somehow co-signed.
Implementations vary in coordination model and privacy guarantees. Wasabi and Samourai (now sanctioned) used central coordinators; JoinMarket pays liquidity providers in a market; Whirlpool used fixed-denomination pools. None hide the fact that a CoinJoin happened — the on-chain pattern is recognizable — but they obscure the input-to-output mapping within the round.
CoinJoin is legal in most jurisdictions and was the dominant Bitcoin privacy technique for years. Tornado Cash sanctions and the 2024 takedown of Samourai's coordinator chilled the space significantly.