A Custodial Exchange lets customers buy, sell and store bitcoin. The operator or its appointed custodian manages the private keys: secret values used to create digital signatures that authorize spending. The customer gives instructions through an account but cannot sign the transaction independently of the service. Their legal rights to the assets depend on the agreement and applicable law.
Anna buys bitcoin and sees 100000 sat in the app: one hundred thousand of bitcoin's smallest commonly used units. She can sell them on the exchange, but she does not have the keys to send the bitcoin to the network herself. The exchange or its custodian manages those. Bitcoin's base layer works with UTXO, transaction outputs that have not yet been spent; spending them usually requires a signature made with a private key. Each output specifies an amount and the conditions for spending it. An exchange login password is not that key. The balance represents what the service records for Anna. By itself, it does not tell her which assets back it or what rights she would have if the company ran into trouble. [1] [5]
An exchange can match a buyer's order with a seller's offer. The collection of bids and offers is called an order book. Once a trade takes place, the exchange changes its records: one customer gains a bitcoin balance, another a money balance. Each trade need not create a new transaction on the Bitcoin network. That is why trading inside an exchange may feel instant while withdrawing to your own wallet takes longer. The price, the gap between buy and sell offers and the fee all affect the outcome. A completed trade confirms a purchase under the platform's rules, not a transfer of keys into Anna's control. [3]
If Anna sends bitcoin from her wallet to the exchange, she uses the deposit address shown in her account. She also checks the supported network and any minimum amount. A token named after bitcoin on another network is not the same as BTC on Bitcoin's base layer. Exchanges usually wait for a certain number of confirmations. The first means that the transaction has entered a block; each subsequent block built on top adds another confirmation. An internal review can also delay crediting. The transaction identifier, txid, helps locate the transfer but does not itself prove that Anna's account has been credited correctly. Equally, a later move into the exchange's shared wallet does not automatically mean that her balance has disappeared. [5] [7]
When Anna requests a withdrawal, she first asks the service to send the bitcoin. The exchange may have limits, a waiting period, an approved-address list or identity checks. Only after it creates and broadcasts a transaction can that transaction be followed on the network. Suppose the service deducts a 1000 sat withdrawal fee from the requested 100000 sat: her wallet receives 99000 sat. This is an example, not a fee schedule. The customer's fee need not equal the mining fee either; the exchange may combine several withdrawals in one transaction. Anna checks the network, destination address, amount and confirmations in her own wallet. A withdrawal through Lightning Network uses a network of payment channels, where participants update how funds are divided without recording every payment separately on the main chain. [8] [9]
Control of keys and legal ownership are different matters. Depending on the custody arrangement and applicable law, a customer may retain ownership rights even though a custodian executes transfers. Other arrangements may create a claim against the company. No single description fits every exchange. Separating customer property from company property, called segregation, and keeping reliable records of each customer's share matter. A shared wallet is not, by itself, proof of misappropriation. It is also worth reading whether the product is genuinely safekeeping or allows assets to be lent or pledged. Such use must comply with applicable law; a sentence in a contract does not automatically make it lawful. [3] [2] [6]
Some funds may be available for routine withdrawals through a Hot Wallet, whose keys are used in an internet-connected environment. Cold Storage limits their exposure to online systems. Multisig requires several signatures; MPC (Multi-Party Computation) distributes a cryptographic computation among several participants. In this kind of signing, separate participants jointly produce a signature without assembling the entire private key in one place. These methods can reduce certain risks, but none of the labels guarantees honest accounts or safe operations. Staff permissions, backups, recovery and transfer checks matter too. If the exchange uses another custodian, there is another link in the chain of responsibility. Anna should know who is involved in holding her assets rather than settle for a picture of a vault. [1] [10]
Solvency means, in simplified terms, that the value of assets covers liabilities. Liquidity is the ability to meet payments and withdrawals on time. A company may own valuable assets that are not readily accessible. Another may temporarily pay customers from new deposits while concealing a shortfall. Large numbers of withdrawals can quickly expose these weaknesses. But a technical incident, attack or banking problem can also halt withdrawals. A delay alone therefore does not establish insolvency, just as one successful withdrawal does not establish lasting financial health. This is counterparty risk in practice: the outcome also depends on the other party meeting its obligations. [1] [4]
An exchange may publish Proof of Reserves. Depending on the method, this can demonstrate control of certain bitcoin at a particular moment. Some systems also use a Merkle Tree, a structure for checking that a record is included in a list, for customer balances. Anna may then verify that her account is included, but not automatically that the list contains every company liability. Reserves may be temporarily borrowed, assets pledged and some debts omitted. An advisory from staff at the PCAOB, the US body overseeing audits of public companies, therefore distinguishes these reports from financial statement audits. Even a genuine audit is not a promise of future safety. The scope, period and exact company examined all matter. [4]
Exchanges often carry out KYC, meaning identity checks and understanding their customers, and link those details with trades, bank transfers and Bitcoin addresses. A database leak can expose sensitive financial connections. Security checks, legal obligations or disputes over the terms may restrict account access. Bitcoin's rules have not changed, but Anna may still be unable to withdraw. A strong password and multi-factor authentication, such as an additional login approval, help prevent account takeover. They do not solve missing reserves or an operator's failure. Choosing a service therefore also involves understanding complaints and the procedure for a blocked account. [1]
Anna first checks the exact company she is contracting with, its supervision and its custody and withdrawal rules. An insurance logo is not enough: she needs to know what is covered, who receives compensation and which exclusions apply. A small deposit and withdrawal can help her learn the process and fees, but cannot guarantee future performance. If she wants control herself, she prepares and safely backs up a wallet, verifies its receiving address and starts with an appropriately small test. She never gives the exchange that wallet's Seed Phrase, the words used to restore it. Self-custody removes reliance on the exchange for the withdrawn funds but makes Anna responsible for the keys. The point is to understand both options and not mistake a convenient account for control she does not actually have. [1] [3]
For the clearest picture, read this entry together with Self-custody, KYC, Proof of reserves, Counterparty risk, Bitcoin, UTXO. The reverse links also lead from KYC, Dollar-cost averaging (DCA), Spot Bitcoin ETP, Brian Armstrong.