What is CoinJoin in Bitcoin?

CoinJoin is a privacy technique in which several Bitcoin users build one shared transaction. Because many inputs and many similar-looking outputs sit in the same transaction, an observer cannot easily tell which coins went where. It works with Bitcoin as it is, with no protocol changes.

How does CoinJoin work in Bitcoin?

The Bitcoin Wiki, describing the idea Gregory Maxwell proposed on the Bitcointalk forum, lays out the basic steps. Participants agree on a set of inputs to spend and a set of outputs to receive. Each person signs only their own inputs. The signatures are then combined, and the transaction is invalid until every signature is present.

To blend outputs together, participants usually agree on a uniform output amount, with any extra going to separate change outputs. Since no one signs a transaction they disagree with, no participant can steal from another.

The Wiki also lists limits. IP addresses can leak unless users connect over a network like Tor. A participant can disrupt a round by refusing to sign. And the privacy gained is capped by how many people join. For the wider context, see what is a UTXO and can cryptocurrency be traced.

What is a CoinJoin coordinator?

Many implementations use a coordinator, a server that gathers participants and assembles the shared transaction. According to the Wiki, a coordinator cannot steal funds, but depending on the design it may learn which inputs map to which outputs.

Bitcoin Optech's history of the topic traces Maxwell's 2013 proposal through JoinMarket in 2015, which pairs "takers" with "makers" who earn fees for supplying coins, to coordinator-based designs such as Wasabi Wallet and Samourai's Whirlpool. Wasabi 2.0 adopted a protocol called WabiSabi in 2022 that allows varied output amounts.

Which wallets offer CoinJoin?

Optech lists JoinMarket, Wasabi Wallet and Sparrow Wallet among implementations, and Samourai's Whirlpool historically. Availability has changed. zkSNACKs, the company behind Wasabi, announced it would stop running its coordination service on June 1, 2024, according to No Bullshit Bitcoin. The report said the change also affected other clients that used that coordinator, naming Trezor Suite and BTCPay Server. Wasabi continued as a regular wallet.

Is CoinJoin legal?

The technique itself is a type of transaction, and laws differ by country. What has drawn enforcement is the operation of mixing services. The US Attorney's Office for the Southern District of New York said that in November 2025 Samourai Wallet's CEO Keonne Rodriguez and CTO William Lonergan Hill were sentenced to five and four years in prison. Prosecutors said they took part in a conspiracy to operate a money transmitting business that transmitted criminal proceeds, and alleged that more than $237 million in criminal proceeds moved through the service. Our guide to crypto mixers covers mixing services more broadly.

Rules differ by country and change often. Check the regulator or a qualified professional for your own situation.