Crypto mixers, also known as Bitcoin tumblers (even tho they can support a wide variety of crypto assets, including ERC-20 tokens), allow users to transact with their cryptocurrencies privately. They work by pooling together funds from different sources and then allowing users to withdraw from the pool to a destination address of their choice. Since the funds are lumped together and then distributed at random times, examining the trails behind exact coins and their new destinations becomes particularly hard, helping users gain privacy. The dynamics of crypto mixers can be explained through an analogy: If you take ten $100 notes from ten people and put them all together in a bag, it is unlikely that each person will have the same note they put in if you ask them to retrieve their notes. If you then play around with factors such as the order of retrieval, where notes are delivered, in what order and at what times, it becomes even more difficult to track the transaction trail of an exact note. Bitcoin tumblers follow a similar model. If more people contribute, it gets progressively harder to trace which note originally belonged to whom. Crypto or Bitcoin mixers create private pools and muddle them before sending coins out to pre-set recipient wallets. There are two main types of cryptocurrency mixers. They are sufficiently different, although they stay true to the founding idea of how Bitcoin mixers work. Centralized mixers (tumblers) will receive your Bitcoin or tokens and send it to a designated address for a fee. Decentralized mixers are built on the blockchain and use a protocol to receive and send identical amounts of Bitcoins or tokens. They usually use a peer-to-peer or coordinated approach and involve many people, usually in the hundreds.