What Is a Decentralized Exchange (DEX)?

A DEX is a crypto exchange that runs on smart contracts, letting users swap tokens directly from their own wallets without a company holding their funds. Instead of opening an account, you connect a wallet, choose two tokens and approve the trade. The code then settles it on the blockchain.

DEXs are one of the main building blocks of decentralized finance. If DeFi is new to you, start with the guide to what DeFi is. This guide explains how DEXs work, what they cost, how they compare with centralized exchanges and buying services, and what can go wrong. Facts about specific DEXs are as of September 2026.

Many DEXs run on Ethereum and on networks built around it, where every swap needs a little ETH to pay the network fee. To check what ETH costs today, see the Ethereum price and payment options.

What is a DEX?

A DEX is a marketplace for crypto tokens that runs as code on a blockchain, not as a company. It fills your order from a pool of tokens or from other users’ orders, and you sign each step in your wallet.

The key difference from a centralized exchange is custody, meaning who holds the crypto. On a centralized exchange, you deposit funds into an account the company controls. On a DEX, your tokens stay in your own wallet until the swap, and the smart contract sends the new tokens straight back to it. As ethereum.org puts it, you “never give up control of your assets”.

Control comes with responsibility. There is no password reset and no support desk that can reverse a trade. Most DEXs also only swap one crypto token for another, so people usually turn dollars or euros into crypto somewhere else first.

How does a DEX work?

Most DEXs work in one of two ways: you trade against a pool of tokens, or your order is matched with other users’ orders in an order book. DEX aggregators sit on top of both and search many DEXs for a good rate.

Liquidity pools and automated market makers

The most common design is the automated market maker (AMM), made popular by Uniswap. Each pool holds two tokens, for example ETH and a dollar stablecoin such as USDC. When you swap, you add one token to the pool and take the other one out.

A formula sets the price. In Uniswap’s classic design it is x × y = k: the two token balances multiplied together must stay the same. Taking ETH out of the pool leaves less ETH in it, so each extra unit costs a little more. Uniswap’s documentation notes that larger trades move the price more than small ones. This is called price impact.

The tokens in each pool come from liquidity providers (LPs), who deposit pairs of tokens and earn the swap fees traders pay. LPs carry a risk called impermanent loss: when prices move, they can end up with less value than if they had simply held their tokens.

Order books

Some DEXs use an order book, like a traditional exchange. Buyers and sellers post orders at the prices they want, and the system matches them. Keeping every order on a blockchain needs a fast network, so these DEXs often run on their own chain. Hyperliquid, for example, runs its own blockchain with fully on-chain order books.

DEX aggregators

A DEX aggregator does not hold pools of its own. It compares prices across many DEXs and pools, then routes your swap, sometimes in several parts, to get a better overall rate. Jupiter plays this role on Solana, and 1inch, 0x and CoW Swap are among the aggregators used on Ethereum and other networks, according to DefiLlama. Your wallet still approves the final transaction, so check the tokens and amounts before you sign.

What fees do you pay on a DEX?

Most DEX swaps carry two costs: a swap fee that goes to the pool’s liquidity providers, and the blockchain’s network fee. Some websites that connect you to a DEX add a charge of their own, so check the final amount your wallet shows before you confirm.

• Swap fee. Each pool sets its own fee. Uniswap’s documentation says swap fees are “configured by pool and protocol version” and are paid to liquidity providers. Since Uniswap v4 (January 2025), a pool can also be created with dynamic fees that change from swap to swap.
• Network fee. Every swap is a blockchain transaction. On Ethereum this fee is called gas, and ethereum.org states that it has to be paid in ether (ETH). On Solana, fees are paid in SOL. Network fees rise when the network is busy.
• Approvals. Before your first swap of a token, you usually approve the DEX’s contract to spend it. That approval is a separate transaction with its own network fee.

DEX vs centralized exchange vs buying service: what is the difference?

The main differences are who holds your crypto, whether you prove your identity and what you can pay with. A DEX swaps tokens you already hold. A centralized exchange holds your funds in an account. A buying service turns money into crypto and sends it to a wallet.

Many people combine them. They buy crypto with money on an exchange or buying service, move it to a self-custody wallet, and then use a DEX to swap it for other tokens.

What are the risks of using a DEX?

The biggest risks are faulty or malicious code, fake tokens, bad prices and simple mistakes. A DEX has no deposit insurance, and a confirmed transaction usually cannot be reversed.

• Bugs and hacks. Attackers exploit mistakes in smart contracts. Chainalysis counted $3.1 billion stolen from DeFi protocols in 2022, 82.1% of all crypto stolen by hackers that year. In December 2025 it reported that DeFi hack losses had stayed relatively low in 2024 and 2025, but hacks still happen.
• Rug pulls and fake tokens. Anyone can create a token and a pool for it. In a rug pull, the creators promote a new token and then drain its pool. Chainalysis notes that code audits are not required to list a token on most DEXs. Scammers also copy well-known token names, so check the contract address with an official source.
• Slippage. The price can move before your swap is confirmed, and large trades in small pools move it further. A slippage tolerance makes the swap fail if the price moves more than you allow.
• Front-running bots (MEV). Bots watch pending transactions and trade just before and after yours, a tactic called a sandwich attack. Ethereum.org says sandwiched users face “increased slippage and worse execution on their trades”.
• Wrong network. The same token can exist on several blockchains. Sending it on a network the receiving wallet or service does not support can make it hard or impossible to recover. Moving tokens between networks needs a bridge, and ethereum.org notes that many of the largest blockchain hacks involved bridges.
• Fake websites and harmful approvals. A copy of a real DEX site can ask you to approve a contract that drains your wallet. Use a bookmark, and read how phishing attacks work.

Do DEXs require KYC?

Most DEXs do not ask for identity documents, because you connect a wallet instead of opening an account. That does not make DEX trading anonymous or place it outside the law. Every swap is recorded on a public blockchain and linked to your wallet address, and the rules that apply depend on where you live and on how each service is run:

• European Union. Under the Markets in Crypto-Assets Regulation (MiCA), crypto services provided “in a fully decentralised manner without any intermediary” are out of scope. Whether a platform is fully decentralised is assessed case by case by the competent authorities (ESMA, as of September 2026).
• United States. The US Treasury’s 2023 DeFi risk assessment says DeFi services doing activity covered by the Bank Secrecy Act have anti-money-laundering duties “regardless of whether the services claim” to be decentralized.
• DEX websites. The company behind a DEX website can screen who uses it. Uniswap Labs announced in April 2022 that its app blocks wallet addresses linked to sanctions, stolen funds and ransomware.

Identity checks usually come in when money is involved. To turn dollars or euros into crypto, people normally use an exchange or buying service that checks who they are, and providers that send crypto for customers may also have to follow the travel rule. Read KYC and crypto to learn why these checks exist. Swapping tokens can also have tax consequences; see crypto taxes before you buy.

What do you need to use a DEX?

You need a self-custody wallet that supports the DEX’s network, the tokens you want to swap, and some of the network’s own coin to pay fees. On Ethereum, that coin is ETH. These steps help keep any mistake small:

What are the most popular DEXs?

As of September 2026, Uniswap is the largest DEX by trading volume. In the 30 days to 29 September 2026, it handled roughly a third of all the DEX volume that DefiLlama tracks, and PancakeSwap came second. Rankings change often, so treat this list as a snapshot, not a recommendation.

Uniswap’s governance token, UNI, has its own Uniswap (UNI) page, and What is Uniswap? explains the protocol in more detail. Before you use any DEX, check that it supports your network and token, and learn how it works.

Frequently asked questions

Malcolm O'Mahony

Malcolm is a Content Marketing Manager at Coinmama. He's passionate about Web3 and specializes in making complex concepts easy to understand. Crypto since 2017. Coinmama since 2020.

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