A crypto exchange is a service or protocol that lets people trade one crypto asset for another, and in many cases trade crypto for fiat currency such as U.S. dollars or euros. Most people use a centralized platform, where a company runs the order matching, holds customer balances, and processes withdrawals. Decentralized exchanges do the same basic job with smart contracts on a blockchain, so the operator’s role is much smaller or absent. The practical difference lies in who controls the assets and the trading system, and that difference shapes your costs and risks.
What a crypto exchange actually does
An exchange brings buyers and sellers together and gives them a way to convert one asset into another. The word “exchange” describes the function, not a legal category. A single company may act as an exchange, a broker that executes trades for you, a custodian that holds your assets, and a market maker that quotes prices against your orders. The U.S. Securities and Exchange Commission (SEC) has described crypto platforms that combine these functions, and it has warned that combining them can create conflicts of interest. Before using any platform, find out which roles it plays for your account.
How a typical centralized trade works
The steps below describe a common workflow on a centralized platform. Menus, verification requirements, and order types differ from one service to another.
- Open and verify an account. Most platforms require an email address, a password, and two-factor authentication. Many also require identity verification before you can deposit or trade larger amounts.
- Fund the account. You can usually deposit fiat currency by bank transfer or card, or you can send crypto from another wallet or account to a deposit address the platform shows you. Confirm the asset and network before sending, because sending the wrong asset or using the wrong network can cause loss.
- Choose a trading pair. A pair such as BTC/USD means you are buying or selling bitcoin against U.S. dollars. Some platforms show the pair in a “Markets” or “Trade” menu, and the order screen shows the current price.
- Submit an order. A market order executes at the best available price at the time, while a limit order sets the maximum you will pay or the minimum you will accept and may not fill. Check the estimated total, including fees, before you confirm.
- Read the balance update. The platform’s internal ledger reflects the trade, and your account now shows the new asset balance. In many centralized trades, the trade is recorded inside the platform’s own system rather than as a separate transaction on a public blockchain.
- Withdraw if you choose. To move crypto out, you enter a destination address, pick a network, and pay any withdrawal fee. The platform then broadcasts an on-chain transaction, which has its own network fee and confirmation time. Withdrawal rules, minimums, and supported networks are set by each provider.
Not every platform follows this exact sequence. Some route orders to outside liquidity providers, some offer instant conversion without an order book, and some hold assets in arrangements that limit withdrawals. The workflow is a useful map, not a promise about any particular service.
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Centralized and decentralized exchanges compared
A centralized exchange (CEX) is operated by an organization that provides the platform and may run accounts, custody, order matching, and other services. A decentralized exchange (DEX) uses smart contracts on a blockchain to swap assets, usually from a user’s own wallet. The table below summarizes the main differences.
| Feature | Centralized exchange | Decentralized exchange |
|---|---|---|
| Who operates it | A company or organization | Smart contracts; there may be no single operator, though front-end websites are often run by a team |
| Who holds the assets during trading | Usually the platform, in a custodial account | Usually the user’s own wallet until the swap, though some designs require depositing funds into a contract |
| Who controls the private keys | Usually the platform for account balances | The user, through the wallet they connect |
| Account recovery | Possible through the provider’s support process, subject to its verification rules | Not available from a provider; a lost recovery phrase generally means lost access |
| Typical costs | Platform fee, spread, deposit and withdrawal costs | Protocol or liquidity fees, plus blockchain network fees on every transaction |
| Identity checks | Often required | Generally not required by the protocol itself, though the front end or local rules may differ |
The comparison is a general pattern. Individual services vary, and the table does not describe a specific named provider.
Order-book DEXs
Some decentralized exchanges use an on-chain limit order book. Users place buy and sell orders recorded through smart contracts, and matching happens according to the protocol’s rules. Because each order and match can involve blockchain transactions, network costs and confirmation times can affect execution. Some designs run part of the matching off-chain and settle the final result on-chain, which changes the speed and fee profile.
Automated market makers
An automated market maker (AMM) does not match buyers with sellers. Instead, it holds a pool of two or more assets supplied by liquidity providers and prices trades with a predefined formula. The price moves as the pool’s balance changes. This makes trading possible without an order book, but it introduces price impact: a large trade relative to the pool can execute at a noticeably worse price than the quoted rate. Liquidity providers can also lose value relative to simply holding the assets when prices diverge, a risk often called impermanent loss.
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Custody is the question of how and where crypto assets are stored and who can access them. The SEC’s Office of Investor Education and Assistance makes a point that many beginners miss: a wallet does not hold the coins. As the agency puts it in Crypto Asset Custody Basics for Retail Investors (Dec. 12, 2025), “Crypto wallets do not store crypto assets themselves; instead, they store the ‘private keys’ or passcodes for your crypto assets.” The assets exist on a blockchain. The private key is what authorizes moving them.
That distinction leads to two custody models.
Third-party custody on a centralized exchange
When you hold crypto in an exchange account, the platform typically controls the keys. Your balance is a claim recorded in the provider’s system, and you access it through the platform’s login and withdrawal process. This has real advantages: login recovery, customer support, and simpler transactions. It also creates dependence on the provider’s security, solvency, and continued operation. The SEC bulletin notes that third-party custodians, including exchanges, control access to keys, and it advises asking about transaction fees and asset-transfer fees along with other account charges.
Self-custody with a wallet you control
In self-custody, you hold the private keys or the recovery phrase that generates them. You are responsible for backing it up, keeping it secret, and protecting the device or software that uses it. A hot wallet is connected to the internet, which makes it convenient for frequent transactions and more exposed to online attacks. A cold wallet, often a hardware device, is generally less convenient and less exposed to online threats, but it can be lost, damaged, or stolen. If a recovery phrase is lost, the assets can be permanently inaccessible. Never share a private key or recovery phrase with anyone, including a support agent who asks for it.
What trading really costs
The fee shown on the order screen is rarely the full cost. Check each component separately, because a platform with low headline fees can still be expensive on spreads or withdrawals.
- Platform or trading fee. A percentage of each trade, often tiered by volume or by whether your order adds or removes liquidity from the book.
- Spread. The gap between the buy and sell price. On a platform that quotes a single price, the spread is built into that quote.
- Price impact. On a thin market or a small AMM pool, a large order moves the price against you before it fully fills.
- Deposit and withdrawal costs. Bank transfer fees, card fees, and fixed or percentage withdrawal fees set by the provider.
- Blockchain network fees. Charged by the network for each on-chain transaction, including withdrawals and every transaction on a DEX. These vary with network congestion and are not set by the exchange.
Read the fee schedule for the specific service and the network you plan to use before you act. Fee structures change, so check the provider’s current published terms rather than relying on an article’s example.
Risks to understand before using an exchange
Crypto exchanges carry several distinct risks, and they do not all disappear when you move to a different model.
- Price volatility. Crypto prices can move sharply in short periods, and a market order can execute far from the price you saw a moment earlier.
- Illiquidity. Some assets have few buyers and sellers, so you may not be able to exit at a fair price when you want to.
- Cyber threats. Platforms and wallets are targeted by hacks, phishing sites, and fake support accounts. Enable two-factor authentication, bookmark the correct web address, and never approve a transaction you do not understand.
- Outages and withdrawal limits. Platforms can go offline during high volume or maintenance, and some may restrict withdrawals during stress events.
- Conflicts of interest. When one company runs the exchange, the broker, and the custody, it may have incentives that conflict with yours. The CFTC notes that platforms trading from their own accounts is itself a risk in virtual-currency cash markets.
- Provider failure. A centralized provider can fail, and customers may be treated as unsecured creditors. Recovery is not guaranteed.
- Smart-contract and user error on DEXs. Decentralization does not remove the risk of bugs in contract code, malicious tokens, or sending funds to the wrong address.
Regulation and protections: what varies
Rules for crypto exchanges depend on the country, the type of product, and the activity. The points below describe U.S. agencies and the product categories their materials address, and they should not be read as a worldwide statement.
- SEC. The SEC’s investor alert warns that crypto-asset entity accounts do not receive the same protections as securities held with registered broker-dealers or deposits at insured banks. That statement concerns U.S. protections and crypto-asset entities. It does not mean every asset or every jurisdiction lacks protection, and it does not mean any given platform is or is not insured.
- CFTC. The Commodity Futures Trading Commission has primary oversight of commodity derivatives, such as futures and certain leveraged products. Its oversight of spot commodity cash markets is limited. Leverage amplifies losses in derivatives, so it is a separate risk from spot trading.
- Other jurisdictions. Outside the United States, regulation differs widely. Some countries license exchanges directly, some restrict access, and some have no specific regime. Check the rules where you live and the registration status of the platform you intend to use.
Proof of reserves: a useful but limited claim
Many platforms publish proof-of-reserves reports showing that they hold certain assets. These reports can be informative, but they answer a narrower question than many readers assume. The SEC investor alert notes that a proof-of-reserves report may be a point-in-time snapshot, and it may not reveal liabilities, activity between snapshots, or the priority of creditors if the entity fails. The alert also states that proof of reserves is not as rigorous or comprehensive as a financial statement audit. Treat such a report as one input among several, alongside the provider’s audited financial statements, if it publishes them, and its terms of service.
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A practical checklist before you open an account
- Identify the roles the company plays: exchange, broker, custodian, or market maker.
- Confirm whether your balance is held in custody or in a wallet you control, and read the terms on withdrawals and account recovery.
- Check which assets, networks, and jurisdictions are supported, and whether the platform is registered or licensed where you live.
- Compare the full cost of a trade, including spread, price impact, transfer fees, and network fees.
- Test with a small withdrawal to confirm the address, network, and fee before moving a larger amount.
- Enable two-factor authentication and store your recovery credentials offline.
This is a general explainer, not personalized investment, tax, or legal advice. If a platform asks for a private key, a recovery phrase, or payment to “unlock” a withdrawal, stop and verify the request through the provider’s official channels.
A crypto exchange is a trading service, and the most important question about it is who controls the assets and the trading system at each step. A centralized platform offers convenience and recovery options in exchange for relying on the provider. A decentralized exchange shifts control and responsibility to you and to the smart contracts you use. Understanding that trade-off, and the costs and risks attached to each model, is the foundation for choosing well.
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