Chainalysis is a Danish blockchain compliance company founded 2014, the absolute leader in this space. Adopted by nearly all major crypto exchanges (Coinbase, Binance, Kraken), traditional banks, and regulatory/law enforcement agencies (FBI, IRS, EU regulators, US Treasury OFAC) for crypto AML compliance. Core products: (1) KYT (Know Your Transaction) — exchanges check address risk on every transaction, rejecting hits on darknet/ransomware/sanctioned addresses; (2) Reactor — forensics tool visualizing fund flows from source through mixers to exchanges; (3) Address screening API — single-query risk scoring for any address. Competitors include TRM Labs, Elliptic, but Chainalysis has the most complete database (years of crawling and intel partnerships). Typical developers don't access it, but all compliance-grade crypto product backends use Chainalysis.