Cryptocurrency tumblers (also known as mixers) provide a custodial mixing service where a user deposits cryptocurrency to be mixed for privacy reasons. Although coin mixing doesn't guarantee complete privacy, it makes tracing transactions more difficult. These services are sometimes used to launder "dirty coins," which are garnered through criminal activity. This is done by mixing dirty coins with coins from different wallets, then transferring the "cleaned" coins to another wallet. While cryptocurrency mixers are also used for non-criminal purposes, some countries have cracked down on their use altogether. Service providers typically charge a 1-3% fee for this type of service. These services seem to be waning in popularity as newer, non-custodial options have appeared.
