custodial wallet

A custodial wallet is one where a third party — typically an exchange or a fintech app — holds the private keys on your behalf. From your side it feels like a bank account: you log in with a password, you see a balance, and you can reset access if you forget your credentials. Under the hood, though, the keys that actually control the on-chain funds belong to the custodian, and your 'balance' is a database entry recording what they owe you.

This design buys genuine convenience. There is no seed phrase to lose, recovery is a customer-support flow rather than an irreversible catastrophe, and the custodian can offer features like fiat on-ramps, account freezes for fraud, and instant internal transfers that never touch the chain. For many newcomers and for businesses needing regulatory compliance, that managed experience is the point.

The cost is counterparty risk and loss of control, summed up in the phrase 'not your keys, not your coins'. Because the custodian controls the keys, they can freeze your account, be ordered to seize funds, get hacked, or — as repeated collapses like Mt. Gox and FTX showed — become insolvent or fraudulently lend out customer assets, leaving holders as unsecured creditors. You are also trusting that the on-chain reserves truly back every database balance, which proof-of-reserves attestations attempt, imperfectly, to demonstrate.