Custody

Custody is the question of who actually holds and controls the private keys to cryptocurrency, and therefore who can move it. Every arrangement for holding crypto falls somewhere on this spectrum: self-custody, where you hold your own keys; third-party custody, where an exchange or specialist custodian holds them for you; and hybrid setups such as multisig or collaborative custody, where control is split between parties.

The distinction matters because on a blockchain, possession of keys is control of funds, with no built-in recourse. For example, an investment fund offering a bitcoin ETF does not keep coins on a laptop; it uses a regulated custodian such as Coinbase Custody, which stores keys in audited cold-storage systems with insurance, access controls, and segregated client accounts. An individual holding the same bitcoin on a hardware wallet has taken the opposite approach, accepting personal responsibility in exchange for eliminating the custodian as a point of failure.

Custody is also where regulation concentrates, since custodians hold client assets the way banks hold deposits; licensing regimes and proof-of-reserves practices grew out of exchange failures in which customer funds turned out to be missing. A common misconception is that assets shown in an exchange account are yours in the way on-chain coins are; they are a claim against the custodian, which is exactly why the industry repeats the phrase not your keys, not your coins. Choosing a custody model is the most fundamental security decision a crypto holder makes.