CoinJoin
CoinJoin is a Bitcoin privacy technique where multiple users combine their transactions to break UTXO linkability for outside observers.
In CoinJoin, 5-100 users combine into one large transaction. Each contributes similar amounts and receives similar amounts — but which input matches which output is indeterminable to outside observers. Wallets like Whirlpool (Samourai), Wasabi and JoinMarket automate this. Controversy: regulators sometimes view CoinJoin as a money-laundering tool, while users see it as normal financial privacy.
Example
Alice mixes 0.1 BTC with 9 others in a CoinJoin. After the tx she has 0.1 BTC again (minus fees), but external chain analysis cannot tell if her new UTXO came from her original or from another participant.
Frequently asked questions
Is CoinJoin legal?
Privacy is legal, CoinJoin in principle too. But some exchanges flag CoinJoined coins as risky. In 2024 Samourai Wallet faced US prosecution — regulatory risks are real.
Related terms
Further reading
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