SAFU — "Secure Asset Fund for Users" — is Binance's self-insurance fund, established in July 2018 and funded from a share of trading fees, now worth roughly $1 billion and, according to Binance, held in bitcoin. It is a fund the exchange holds to cover unexpected user losses from security incidents or platform failures. The name became a meme ("funds are safu") before becoming an actual fund.
What SAFU has actually been used for
The best-known invocation came in May 2019: attackers exfiltrated 7,000 BTC from a Binance hot wallet (about $40M at the time). Binance announced the same day that SAFU would cover the incident in full and that no user funds would be affected. This was the first major test and it worked.
What SAFU is not
SAFU is not FDIC insurance. There is no statutory obligation to cover losses; the fund is deployed at Binance's discretion, on its own timeline, for whatever portion of the loss it chooses. The May 2019 incident set a precedent of "full coverage, fast" but no contract requires that for future incidents.
SAFU also does not cover user error. Lose your private key, get phished into signing a malicious transaction, send funds to the wrong address — none of these are SAFU events. The fund covers platform-side incidents, not user-side mistakes.
The competitor positions
Other large exchanges describe their reserves and loss-coverage arrangements in their own terms, and not all of them run a separately named fund like SAFU. Read each exchange's own disclosure rather than assuming an equivalent exists.
For a US-resident holder comparing exchanges, SAFU is a positive signal but not a complete one. The combination "regulated exchange + PoR + self-insurance fund" is what to look for. Binance.US, Coinbase, and Kraken each clear different parts of that combination.
How to use this in custody planning
SAFU should not change the 30% rule. Even with a roughly $1B insurance fund, you do not want more than 30% of your stack on any CEX, because the fund covers platform-side incidents, not "platform decides to freeze your specific account for compliance reasons." Self-custody addresses both classes of risk; SAFU addresses only one.
Further reading: Proof of Reserves, Exchange evaluation handbook, CEX.