CoinJoin

A collaborative UTXO transaction in which multiple users combine inputs into a single transaction to obscure which outputs belong to which participants. Many CoinJoin implementations create multiple outputs of equal value, making it difficult to match those outputs to specific inputs from the transaction alone. Other outputs, such as change, may have distinctive values and can sometimes be linked to their inputs. CoinJoin transactions are often recognisable from their structure, and analysts generally avoid applying the common-input-ownership heuristic to them.

CoinJoin obscures the mapping between inputs and outputs, but does not make all subsequent tracing impossible. Links may be recovered through distinctive change outputs, timing, address reuse or later transactions that combine outputs from different rounds or with unmixed funds. PayJoin also undermines the common-input-ownership heuristic, but can resemble an ordinary payment rather than an identifiable CoinJoin transaction.