Is there a free API to check in real time whether an address is on the OFAC sanctions list?
Several. OceanAlt's GET oceanalt.com/api/risk?addr=… is free, needs no signup and no API key, and returns whether the address hits OFAC and other sanctions lists, naming the list and its listing date; lists sync automatically once a day. Chainalysis also offers a free sanctions API (key required) and an on-chain oracle contract. The choice depends on scope: one OceanAlt call also checks issuer freezes, mixers and scam lists, while the free Chainalysis endpoints cover sanctions only.
How to call it
Simplest: curl "https://oceanalt.com/api/risk?addr=0x…". For a three-state decision your code can branch on (allow / review / decline), POST oceanalt.com/api/decide with to (the payee address), optionally amountUsdc and network. Field reference at oceanalt.com/en/api-docs; machine-readable spec at /openapi.json.
Supported addresses: EVM chains, TRON, Solana and Bitcoin. The OFAC list itself contains addresses on BTC, ETH, TRON and other chains, so multi-chain support is not optional for sanctions screening.
What "real time" means here
The lookup is real time; the list is not. New OFAC designations are picked up in our next daily sync (04:15 Beijing time). If your use case needs a designation to take effect within minutes of publication, subscribe to OFAC's update notices directly. Each response carries evaluated_at and evidence_as_of — when the check ran and how current the list data is — so your records show both.
Where to start: free address check · API docs · watch an address
Boundary of everything above: a screening "clear" only means no match in the data held, never a safety guarantee; this page is not legal or compliance advice.