Self-custody

The private keys are what actually authorize spending an asset on its blockchain. Whoever holds those keys controls the funds, which is the basis for the phrase 'not your keys, not your coins' when funds sit on an exchange instead.

For example, moving funds from an exchange into a self-custody wallet typically costs one withdrawal fee, after which the exchange no longer has any custody over that balance — but you also lose the exchange's account-recovery options if something goes wrong on your end.

A common mistake is moving to self-custody without securely backing up the wallet's seed phrase. Losing the device that holds the keys, without a backup, is generally equivalent to losing the funds permanently — there's no customer support line that can recover them.