What a mixer actually does
The blockchain is transparent. Every transaction is public. If you send Bitcoin from address A to address B, anyone can follow that thread backward and see where A got its funds, and forward to see where B sends them next. For most purposes, this is fine. For people who want financial privacy, it is a problem.
A mixer solves this by pooling funds from multiple senders and returning equivalent amounts from a different pool. Address A sends 1 BTC into the mixer. Addresses C, D, and E also send 1 BTC each. The mixer returns 1 BTC to each sender, but the returned funds came from the combined pool, not from the original input. The transaction graph is broken.
The legitimate use case was privacy. A journalist in a hostile country, a whistleblower, someone making a legal purchase they do not want associated with their identity. Mixers were the crypto equivalent of paying cash.
The major mixers and what happened to them
Bitcoin Fog (2011-2021)
One of the oldest Bitcoin mixers. Processed approximately 1.2 million Bitcoin over a decade. Seized by the FBI and IRS in 2021. Its alleged operator, Roman Sterlingov, was convicted in 2024 of money laundering conspiracy and sentenced to 12.5 years in prison. All known deposit addresses are in AML databases and score 90 or above.
Helix (2014-2017)
Operated by Larry Harmon, who later pleaded guilty to money laundering conspiracy. Helix processed more than 350,000 Bitcoin and was explicitly marketed to darknet market customers. The DOJ linked it directly to the AlphaBay marketplace. Address set: fully indexed, score 90+.
Chipmixer (2017-2023)
Seized by Europol and the FBI in March 2023. At the time of seizure, it held approximately 1,909 Bitcoin worth about 44 million euros. Another 46 million euros in Bitcoin had already passed through. Chipmixer operated by issuing "chips" of fixed denominations and allowing users to exchange them. Every known chip address is now in AML databases.
Tornado Cash (Ethereum, 2019-2022)
A smart contract mixer on Ethereum. OFAC sanctioned it in August 2022, specifically listing the Tornado Cash smart contract addresses on the SDN list. This was the first time OFAC sanctioned open-source code rather than a person or company. The legal implications are still being contested in court. Using Tornado Cash is prohibited for U.S. persons. Any wallet that interacted with Tornado Cash contracts scores 65 or above, depending on the proximity and amount.
CoinJoin implementations (ongoing)
Unlike the above, CoinJoin is a protocol, not a service. Wasabi Wallet and JoinMarket use CoinJoin to let users mix Bitcoin peer-to-peer without a central operator. These are not sanctioned. But wallets that use CoinJoin frequently still raise AML flags because the behavioral pattern is identical to mixing, regardless of intent.
Why exchanges block mixer-tainted wallets
Exchanges have their own compliance requirements. The Financial Crimes Enforcement Network in the U.S., the Financial Conduct Authority in the UK, and equivalent regulators worldwide require exchanges to have AML programs. Part of that program is not processing transactions for wallets that have used sanctioned services or shown structuring behavior.
The practical consequence is straightforward: if you deposit to an exchange from a wallet with significant mixer exposure, the deposit may be held, your account may be suspended, and you may be required to explain the source of funds before the exchange releases anything.
The threshold varies by exchange and by the strength of the mixer exposure. A small indirect interaction with a CoinJoin output from two years ago is unlikely to trigger a freeze on its own. Direct Tornado Cash contact is a different matter entirely.
Important: Even if you received mixer-tainted funds without knowing it, the burden of explanation falls on you when you try to move those funds through a regulated exchange. "I didn't know" does not prevent account review; it might help resolve it, but the investigation still happens.
How to check for mixer exposure before transacting
Before accepting a payment from an unknown counterparty, or before depositing funds to an exchange that you received from a third party, check the sending wallet address. A quick lookup in @scorechain_amlbot shows mixer exposure as a separate line item in the report, with a distinction between direct interaction and indirect counterparty exposure.
The check takes 8 seconds. The mixer line item tells you whether the wallet directly used a mixer, or whether a counterparty of that wallet did. The score contribution from each is different, and the report makes that visible.
Frequently asked questions
Is using a crypto mixer illegal?
It depends on jurisdiction and intent. Tornado Cash is sanctioned by OFAC, making it illegal for U.S. persons to use. The EU does not specifically ban mixers, but use creates high-risk AML flags. Using any mixer to launder proceeds from a crime is illegal everywhere.
Can I accidentally receive mixer-tainted crypto?
Yes. If someone pays you from a wallet that passed through a mixer, your wallet acquires indirect exposure. A one-hop separation is significant. Three or four hops is small and typically acceptable to most exchanges.
What happened to Bitcoin Fog?
Bitcoin Fog was seized by the FBI and IRS in 2021. Its operator was convicted of money laundering conspiracy in 2024. All known deposit addresses now carry scores of 90 or above in AML databases.
How do I check if a wallet has mixer exposure?
Paste the wallet address into @scorechain_amlbot in Telegram or use the web checker at cryptoaml.ai. The report shows mixer exposure as a separate line item with direct vs indirect exposure flagged.
Check for mixer exposure in 8 seconds
@scorechain_amlbot shows mixer exposure for Bitcoin, Ethereum, TRON, and 12 other chains. Free basic check.
Open @scorechain_amlbot