What is Custody?
Crypto Glossary Definition
Custody refers to the holding of an asset on behalf of a client.
Why Custody Matters
Custody refers to who actually controls the private keys to an asset — "self-custody" means you hold your own keys (via a wallet), while "third-party custody" means an exchange or custodian holds them on your behalf. Every major exchange collapse in crypto history (FTX included) has been, at its core, a custody failure.
Custody in Practice
Consider two crypto users with identical portfolios who make very different choices about where to keep them. The first buys Bitcoin on a major exchange and simply leaves it in her exchange account, trusting the platform to secure the underlying private keys on her behalf — this is third-party custody, convenient because she can trade instantly and never has to worry about losing a recovery phrase. The second withdraws his coins to a hardware wallet he owns, writes down the seed phrase, and stores it somewhere secure; he now has self-custody, meaning only he holds the keys and only he can authorize transactions. The tradeoff becomes obvious the moment something goes wrong: if the exchange in the first scenario is hacked, mismanages customer funds, or becomes insolvent, the custodial user's coins may be frozen or lost entirely, since she never actually controlled them at the protocol level — she held a claim on the exchange's balance sheet instead. The self-custody user bears full responsibility for his own security instead, with no customer support to call if he loses his keys. This exact distinction is why major exchange collapses in crypto history have so often come down, at their core, to a custody failure rather than a flaw in the underlying blockchain itself.
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