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What is a DEX?

Written and maintained by the BTCNATOR editorial team • Last updated September 8, 2026 • How we research

Quick answer

A DEX (decentralised exchange) is a smart-contract application that lets you swap tokens directly from your own wallet, with no account and no company taking custody of your funds. Most DEXs use an automated market maker (AMM): instead of matching buyers and sellers, they price trades against pools of tokens supplied by other users. You keep control of your assets, but you also carry all the responsibility.

How an AMM DEX works

  1. Liquidity providers deposit pairs of tokens (say ETH and USDC) into a pool.
  2. A pricing formula sets the exchange rate based on the ratio of tokens in the pool.
  3. When you swap, your input token goes into the pool and the output token comes out, shifting the ratio and therefore the price.
  4. You pay a trading fee that is shared with the liquidity providers.

Large trades relative to pool size move the price significantly — that is slippage.

DEX vs centralised exchange

  • Custody: DEX – you hold your keys. CEX – the company holds them.
  • Account: DEX – none, connect a wallet. CEX – sign-up and usually identity checks.
  • Recovery: DEX – none; a mistake is permanent. CEX – support may help.
  • Assets: DEX – almost any token on that chain, including brand-new and unvetted ones. CEX – a curated list.

Key facts

  • A DEX is a smart contract, not a company.
  • Most DEXs price trades against liquidity pools, not an order book.
  • You trade from your own wallet and keep custody throughout.
  • Anyone can list a token on many DEXs, so scam and copycat tokens are common.
  • Every swap is an on-chain transaction with a network fee.

Risks and limitations

  • No recovery: wrong token, wrong address or a bad approval is permanent.
  • Malicious token contracts can block selling ("honeypots") or abuse approvals.
  • Low-liquidity pools give bad prices and high slippage.
  • Front-running and sandwich attacks can worsen your execution price.

FAQ

Do I need to register to use a DEX?
No. You connect a self-custody wallet. There is no account and usually no identity check — and no support if something goes wrong.
Why did my DEX trade get a worse price than quoted?
Slippage. The pool price moved between your quote and execution, or your trade was large relative to the pool. Set a slippage limit to cap this.
Are all tokens on a DEX legitimate?
No. Listing is permissionless on most DEXs, so scam tokens and fakes of real projects are common. Verify the contract address from an official source.

Sources

Related topics

What is DeFi?What is a crypto swap?What is a crypto exchange?

This guide provides educational information about how cryptocurrency technology works. It is not financial, investment, legal, or tax advice. Cryptocurrency involves risk, including the potential loss of funds. Please review our editorial policy and methodology for more details.