Every transaction on a public blockchain is permanently recorded and visible to anyone. Wallet addresses are pseudonymous — they are strings of alphanumeric characters with no obligatory link to a real identity — but pseudonymity is not anonymity. Governments and blockchain analytics firms have developed increasingly sophisticated methods for tracing transaction chains and linking addresses to individuals. Mixers exist to complicate that process.

A mixer is an application that breaks the chain of custody between a sender’s wallet and a recipient’s. In a basic smart-contract-based mixer, a user deposits funds from one address into a contract pool, then withdraws the same amount to a different address. The connection between deposit and withdrawal is obscured — the output wallet has no traceable relationship to the input wallet. To improve effectiveness, mixers typically require deposits in standardized denominations and depend on a sufficient number of concurrent users to create a large enough pool that individual transactions cannot be easily disentangled.