What is an AMM in crypto?
An AMM, short for automated market maker, is a smart contract that lets you trade crypto against a pool of tokens instead of against another person. Prices aren’t set by buyers and sellers placing orders, but by a mathematical formula based on how many of each token sit in the pool. AMMs power most decentralized exchanges, such as Uniswap, and they are one of the building blocks of decentralized finance (DeFi).
What is an AMM in crypto?
An AMM in crypto is a type of decentralized exchange protocol that holds two or more tokens in a liquidity pool and quotes a price for swaps automatically. You connect your crypto wallet, choose how much of one token you want to swap, and the smart contract sends you the other token at a price its formula calculates.
On traditional exchanges, a market maker is a firm that always offers to buy and sell, so there is liquidity for other traders. Automated market makers do the same job with code. Instead of a company or centralized intermediaries, the smart contracts and the pool provide continuous liquidity, 24 hours a day, for any token pair someone has set up.
How do AMMs work?
AMMs work with three ingredients: a liquidity pool, a pricing formula and a fee. Here’s what happens behind a single swap:
- Liquidity providers fill the pool. They deposit two tokens, usually in an equal amount by value, for example ETH and a euro stablecoin.
- You send one token in. To buy ETH, you add stablecoins to the pool.
- The formula sets the price. The contract calculates how much ETH it can give back while keeping its formula balanced.
- A fee is taken. A small percentage of your trade stays in the pool for the liquidity providers.
- The price moves. The pool now holds more stablecoins and less ETH, so ETH gets slightly more expensive for the next trader.
If the pool’s price drifts away from the market price on other exchanges, arbitrage traders step in to buy the cheap side and sell the expensive side until prices line up again. That’s how AMMs stay close to the current market price without any central price feed.
The constant product formula
The best-known pricing formula is the constant product formula: x × y = k. Here x and y are the token balances in the pool, and k is a fixed constant that must stay the same after every trade (apart from fees). A pool that follows this rule is called a constant product market maker, and it was popularised by Uniswap.
A worked example in euros
Say a pool holds 10 ETH and 30,000 euro stablecoins. That makes k = 300,000, and the pool’s price for 1 ETH is €3,000.
You want to buy 1 ETH. After your trade the pool may only hold 9 ETH, so it needs 300,000 ÷ 9 = 33,333.33 stablecoins to keep k the same. You pay about €3,333 for that 1 ETH, plus a fee of about €10 at a 0.30% fee level. Your average price is roughly 11% above the €3,000 you saw, because your trade was large compared with the pool. In a pool a hundred times deeper, the same trade would barely move the price.
That gap is price impact, also called slippage. It’s the main thing to check before larger trades on an AMM.
AMM vs order book: what’s the difference?
The difference between an AMM and an order book is who you trade with. On an order book, your order is matched with other users’ buy and sell orders. On an AMM, you always trade against the pool.
| AMM (decentralized exchanges) | Order book (centralized exchanges) | |
|---|---|---|
| Who sets prices | A pricing formula based on token balances | Buyers and sellers placing orders |
| Who provides liquidity | Anyone who deposits tokens | Users and professional market makers |
| Order types | Mostly instant swaps | Market, limit, stop orders |
| Account and KYC | Usually just a crypto wallet | Account with identity verification |
| Best for | Smaller tokens, on-chain trading | Larger trades, euro deposits, tight spreads |
An order book lets sellers offer tokens at a set price and wait. An AMM gives you an instant quote, but large trades in shallow pools get a much lower price. If you want limit orders and euro deposits, a centralized exchange with an order book is usually simpler. Our guide to market and limit orders explains the order types.
Liquidity providers and LP tokens
Liquidity providers are the users who deposit tokens into an AMM liquidity pool. In return they receive LP tokens, a receipt that shows their share of the pool, and liquidity providers earn a share of the trading fees generated by every swap.
Providing liquidity is not a savings account. Your return depends on trading volume, fees and price movements, and it can be negative. Some DeFi protocols add extra token rewards on top, but those rewards often fall in value.
Impermanent loss
Impermanent loss is the main risk for liquidity providers. When the price of one token changes, arbitrage traders rebalance the pool, so you end up with more of the token that fell and less of the one that rose. With the constant product formula, if one token doubles in price against the other, your share of the pool is worth about 5.7% less than if you had simply held both tokens. Fees can make up for that, or not.
Why AMMs matter to you in the EU
For EU residents, the key point is that most AMMs sit outside the investor protection you get at a licensed exchange. MiCA regulates companies that provide crypto services; crypto services provided in a fully decentralised way, without an intermediary, fall outside its scope.
In practice that means:
- No licence, no regulator. If a smart contract is hacked or a token is a scam, there is usually nobody to complain to and no compensation.
- Smart contract risk. A bug in the code can drain a pool. Audits reduce that risk but don’t remove it.
- Fake tokens. Anyone can create a pool for any token, including copies with the same name as a real one. Check the token’s contract address.
- Tax still applies. Swapping one token for another can count as a sale in countries such as Germany, and in the Netherlands your tokens and LP positions count towards box 3 assets on 1 January.
- Network fees. Every swap is a blockchain transaction with its own gas fee, on top of the pool fee.
The future of AMMs in the cryptocurrency ecosystem
AMMs are now a core part of the cryptocurrency ecosystem, and their designs keep evolving. Newer versions let liquidity providers focus their tokens on a price range, use different formulas for stablecoin pairs, or offer several fee levels. Some blockchains, such as the XRP Ledger, have built an AMM directly into the network.
For most people starting out, an AMM is something to understand rather than to use straight away. If you do try one, start with a small amount, use a well-known decentralized exchange, and read up on liquidity pools first.
The bottom line
An automated market maker replaces the order book with a pool of tokens and a formula, so anyone can swap or provide liquidity without a middleman. That openness is the upside and the catch: you get access to more tokens, but no regulator, no compensation scheme, and prices that move against you on larger trades.
Related terms
Questions people ask
What does AMM mean?
AMM stands for automated market maker. It is a smart contract on a blockchain that holds a pool of two or more tokens and quotes prices with a formula, so anyone can swap without a buyer or seller on the other side.
How do AMMs work?
Liquidity providers deposit tokens into a pool. When you swap, you add one token to the pool and take out the other, and a formula such as x times y equals k sets the price based on the pool's new balances. A small fee on each swap goes to the liquidity providers.
What does limit order book mean?
A limit order book is the list of buy and sell orders at set prices that centralized exchanges use. An AMM replaces it with a liquidity pool and a pricing formula, so there are no individual orders to match.
What is the best AMM?
There is no single best AMM. The right one depends on the blockchain you use, the token pair, how deep the pool is and the fee level. Deeper pools give you better prices with less slippage.
How do liquidity providers make money on an AMM?
Liquidity providers earn a share of the trading fees generated by every swap in their pool. Those earnings can be wiped out by impermanent loss when prices move a lot, so returns are never fixed.