A DEX is a decentralised exchange — a smart contract (or set of them) that lets users trade tokens without depositing them with a company first. When you trade on a DEX, the trade executes against a pool of liquidity or an on-chain order book, and at no point does any third party take custody of your assets. The tokens move directly between your wallet and the contract and back out again in a single transaction.
The biggest DEXes today are Uniswap (multichain), PancakeSwap (BNB Chain), Curve (stablecoin-focused), Balancer, Jupiter (Solana aggregator), Raydium, and Trader Joe. They collectively handle something like 15-25% of total crypto trading volume — the majority is still on centralised exchanges — but the fraction has been rising steadily and for certain asset categories (long-tail tokens, newly-launched tokens, stablecoin swaps) DEXes are already the primary venue.
How DEXes Actually Work
Most modern DEXes are automated market makers. Instead of matching buyers and sellers like a traditional exchange, they maintain pools of token pairs and price trades against a formula that keeps the pool balanced. x × y = k is the simplest form, used by Uniswap V2 and its clones. Curve uses a flatter curve for assets that should trade near parity. Uniswap V3 lets liquidity providers concentrate capital in specific price ranges. dYdX and GMX use more order-book-like designs for perpetual futures.
A smaller category of DEXes still run on-chain or hybrid order books. dYdX was one for a while. Serum was one on Solana before it got killed off in the FTX collapse. These work better when block times are fast and fees are low, which is why they tend to show up on chains like Solana rather than Ethereum mainnet.
Where DEXes Win and Lose
DEXes beat centralised exchanges on a few fronts. They are open 24/7 with no account, no KYC, and no deposit/withdrawal friction. They list anything with a pool, which means long-tail and newly-launched tokens are available on DEXes long before they show up on Coinbase. They are censorship-resistant in a way that centralised exchanges cannot match, because there is no operator to take them down. And they compose with the rest of DeFi, so a DEX trade can be part of a larger on-chain transaction that also takes out a loan, provides liquidity, or triggers a smart contract action.
They lose on a few fronts too. Execution is worse for large trades because slippage scales with trade size relative to pool depth. Fees are often higher once you include gas and the AMM’s own swap fee. Price discovery for new assets is noisy in the early hours of listing. And the user experience is still worse than a centralised exchange for anyone not already comfortable with wallets and signing transactions.
Most crypto traders end up using both, picking whichever gives the best execution for the specific trade they are doing. The line between CEX and DEX is also blurring in places — several CEXes now offer on-chain swap integrations, and several DEXes have added KYC-gated access points for institutional flow.