By Saurav Cryptocurrency exchanges work by bringing buyers and sellers together in one place, matching their orders at agreed prices, and recording the swap, either in a company’s own database (on a centralised exchange) or directly on a blockchain through smart contracts (on a decentralised exchange). Most beginners meet the first kind: an app that lets you deposit rupees, buy coins in a few taps, and withdraw later. Behind that simple screen sits a matching engine, a ledger, a custody system, compliance checks, and connections to banks and blockchains. Understanding each moving part makes fees, delays, and risks much easier to understand. This is general information, not investment advice.
Two Main Types of Exchange
- Centralised exchanges (CEXs) are run by companies. They hold your funds, keep an internal record of who owns what, and match trades on their own servers. Examples include the large registered platforms most people use to buy their first coins.
- Decentralised exchanges (DEXs) are run by smart contracts on a blockchain. You trade directly from your own wallet, and no company holds your funds.
- Hybrid models exist too, mixing features of both.
How a Centralised Exchange Works, Step by Step
Step 1: Sign up and verify your identity. Registered exchanges require KYC (know your customer) checks, such as PAN and Aadhaar in India, plus a verification step like a selfie. This is part of anti-money-laundering rules.
Step 2: Deposit money. You add rupees through UPI, IMPS, or NEFT, or add crypto by sending it from another wallet. The exchange credits your account balance.
Step 3: Place an order. You choose a coin, whether to buy or sell, the amount, and an order type.
Step 4: The matching engine pairs orders. The exchange’s software compares buy and sell orders and executes trades where prices meet.
Step 5: Balances update on the exchange’s ledger. The swap is recorded in the platform’s internal database, which is why trades on a centralised exchange are instant and usually don’t pay blockchain fees.
Step 6: Withdraw. You can send rupees to your bank account or move crypto to your own wallet, which does involve a blockchain transaction and its fee.
The Order Book
Most centralised exchanges use an order book, a live list of all open buy and sell orders.
- Bids are offers to buy at a certain price, and asks are offers to sell.
- The spread is the gap between the highest bid and the lowest ask.
- Market orders buy or sell immediately at the best available prices.
- Limit orders specify the price you’re willing to accept and wait in the book until matched.
- Depth describes how many orders sit near the current price, and deeper books mean smoother trading.
A simple illustration: suppose the lowest sell orders are 0.5 BTC at $85,000, 0.5 BTC at $85,010, and 1 BTC at $85,030. If you place a market order to buy 1.2 BTC, it fills as follows: 0.5 at $85,000, 0.5 at $85,010, and the last 0.2 at $85,030. The total cost is about $102,011, an average price of roughly $85,009 per coin, slightly above the best price you saw. That small difference is called slippage, and it grows in thin markets or with large orders.
Who Provides the Liquidity
- Other traders place the orders you trade against.
- Market makers, specialised firms and algorithms, continuously post buy and sell quotes, which narrows spreads and helps keep prices consistent.
- Aggregation on some platforms routes orders to multiple sources to find better prices.
How Exchanges Make Money
- Trading fees, often split into maker fees (for adding orders to the book) and taker fees (for taking existing orders), commonly a fraction of a percent of the trade value.
- Spreads on instant-buy features, where the displayed price includes a margin.
- Withdrawal and deposit fees, where applicable.
- Listing and other services, such as staking programmes, lending, or derivatives.
For example, a 0.1% taker fee on the $102,011 purchase above would be about $102.
How a Decentralised Exchange Works
Most DEXs don’t use order books. They use automated market makers (AMMs) and liquidity pools.
- Liquidity pools: users deposit pairs of tokens, such as ETH and a dollar stablecoin, into a smart contract and earn a share of trading fees.
- A pricing formula: a common design keeps the product of the two token amounts constant. Price moves automatically as people trade.
- Direct from your wallet: you connect your wallet, approve the swap, and the smart contract exchanges your tokens.
An illustration: imagine a pool holding 100 ETH and 250,000 stablecoins, so ETH is priced at 2,500. Buying 1 ETH moves the pool to 99 ETH, and to keep the product constant the pool needs about 252,525 stablecoins, so you’d pay about 2,525, around 1% above the starting price. Buying 10 ETH would require the pool to hold 90 ETH and about 277,778 stablecoins, so you’d pay about 27,778, or roughly 2,778 per ETH, about 11% above the starting price. That price impact is why large trades in small pools cost more, and why liquidity depth matters. Pools also charge a fee on each swap, often a fraction of a percent.
Centralised Versus Decentralised: Key Differences
- Custody: a centralised exchange holds your funds, while on a DEX you keep your own keys.
- Speed and ease: centralised exchanges are typically simpler, with customer support and bank links, while DEXs require a wallet and some technical comfort.
- Fees: centralised exchanges charge platform fees with no per-trade blockchain cost, while DEXs charge network fees (gas) plus pool fees.
- Compliance: registered centralised exchanges require KYC, while many DEXs don’t, though regulation varies and is evolving.
- Assets: DEXs often list new tokens quickly, including very risky ones, while centralised exchanges generally vet listings.
- Risks: centralised exchanges carry platform risk, such as hacks or failures, while DEXs carry smart contract and user-error risk.
What Happens to Your Coins on a Centralised Exchange
- The exchange holds the actual coins, typically in a mix of “hot” wallets for liquidity and “cold” storage for the majority.
- You hold a claim, shown as a balance in your account.
- Proof of reserves reports, offered by some platforms, aim to show that they hold the assets customers are owed.
- Security measures commonly include two-factor authentication, withdrawal address allow-lists, and cold storage.
Compliance and Regulation
- KYC and anti-money-laundering checks are standard on registered platforms.
- In India, exchanges register with the Financial Intelligence Unit (FIU-IND), crypto isn’t legal tender, gains are taxed at a flat rate, and a 1% TDS applies on eligible transactions.
- Rules vary by country and are still evolving, so use platforms that comply with your local requirements.
Key Risks to Understand
- Platform risk: an exchange can suffer outages, hacks, or insolvency.
- Price volatility and slippage, especially during fast markets.
- Phishing and fake apps that imitate real exchanges.
- Thin markets for smaller coins, where prices can swing sharply.
- Leverage: derivatives can cause rapid losses.
- Withdrawal limits or delays during heavy demand or compliance reviews.
Choosing an Exchange: A Practical Checklist
- Regulatory status: is it registered where you live?
- Security record and practices: two-factor authentication, cold storage, and transparent reserves.
- Fees: trading fees, spreads, deposit and withdrawal costs.
- Liquidity: deep order books on the coins you want.
- Rupee on-ramps: convenient, low-cost UPI, IMPS, or NEFT deposits.
- Coin selection: the assets you need, without excessive risk.
- Support and usability: clear help channels and a platform you understand.
- Tax tools: statements and reports that help with filing.
Tips for Using an Exchange Safely
- Turn on two-factor authentication and use a strong, unique password.
- Double-check the website or app before logging in, and beware of look-alikes.
- Start with a small trade to learn the process and fees.
- Use limit orders in fast markets to control the price.
- Withdraw long-term holdings to a wallet you control if you want to reduce platform risk.
- Keep records of every trade, deposit, and withdrawal for tax purposes.
- Never share your login, OTPs, or recovery phrases.
Frequently Asked Questions
Q1. Is my crypto safe on an exchange?
A. Reputable cryptocurrency exchanges use security measures such as cold storage, two-factor authentication (2FA), encryption, and account monitoring. However, keeping crypto on an exchange means relying on the platform to safeguard the assets. Many users therefore keep only the amount needed for trading on an exchange and use self-custody for other holdings.
Q2. Why are trades on exchanges instant but blockchain transfers slow?
A. Trades on a centralised exchange are generally recorded within the exchange’s internal system, so they can be completed quickly. Blockchain transfers, by comparison, must be broadcast to the relevant network and receive the required confirmations, which can take longer.
Q3. What’s the difference between maker and taker fees?
A. A maker places an order that adds liquidity to the exchange’s order book, while a taker executes against an existing order and removes liquidity. Exchanges often charge makers lower trading fees than takers, although the exact fee structure varies by platform.
Q4. What is slippage?
A. Slippage is the difference between the expected price of a trade and the price at which it is actually executed. It can occur when an order is large relative to available liquidity, prices move quickly, or the order must be filled across several price levels.
Q5. Do I need a wallet to use a crypto exchange?
A. You generally do not need a separate wallet to trade on a centralised cryptocurrency exchange, because the platform manages the deposited assets on your behalf. A compatible crypto wallet is required when using many decentralised exchanges or when withdrawing assets to self-custody.