PayJoin
Also · P2EP · BIP78
A PayJoin is a payment where the recipient adds an input of their own, so the transaction no longer reveals who paid whom or how much, while looking perfectly ordinary.
In a normal payment, all inputs come from the payer and 1 output goes to the recipient. Chain analysis relies on that pattern. In a PayJoin, specified in BIP78, the recipient contributes an input too. The output they receive then contains their own coins plus the payment, and the amount actually transferred is hidden.
The result looks like any 2-input, 2-output transaction. There is no mixing signature to spot, which is its strength over CoinJoin. It also poisons the common input ownership heuristic for every transaction, since analysts can no longer assume inputs share an owner. PayJoin needs the recipient’s wallet or server to be online during payment, which has slowed adoption.
In French · PayJoin