What is an Automated Market Maker (AMM)? How it works and why it's central to DeFi

What is an automated market maker?

An automated market maker (AMM) is a decentralized trading protocol that uses liquidity pools and algorithms to facilitate cryptocurrency trades directly between users. Instead of relying on a traditional order book of buyers and sellers, AMMs automatically determine asset prices based on the ratio of tokens in a pool.

Popular AMMs include Uniswap, Curve, and Balancer.

How it works

  1. Liquidity provision: Users deposit pairs of tokens (e.g., ETH and USDC) into a smart contract, forming a liquidity pool.
  2. Pricing algorithm: The AMM uses a mathematical formula, often x × y = k, to determine token prices based on pool balances.
  3. Trading: Other users can trade directly with the pool at algorithmically determined prices.
  4. Earnings for liquidity providers: Liquidity providers earn a share of trading fees in proportion to their contribution to the pool.

What makes AMMs so useful in DeFi

  • Enable 24/7, permissionless trading without a centralized authority.
  • Lower barriers to market participation.
  • Allow anyone to become a liquidity provider and earn passive income.
  • Provide deep liquidity for tokens that might be illiquid on centralized exchanges.

AMM vs order book exchange

FeatureAutomated Market Maker (AMM)Order Book Exchange
Liquidity sourceUser-funded liquidity poolsBuy/sell orders from traders
PricingAlgorithm-basedMarket supply and demand
IntermediaryNone - fully decentralizedCentralized matching engine or broker
AccessibilityOpen to anyone with a crypto walletOften requires account registration

Where AMMs are used

  • Swapping ETH for USDC on Uniswap.
  • Providing liquidity to Curve for stablecoin trades.
  • Token launches using liquidity pool pairs instead of traditional listings.

FAQs

  1. Do AMMs eliminate price slippage?: No — large trades relative to pool size can still cause slippage.
  2. Can anyone provide liquidity?: Yes — but liquidity providers should be aware of impermanent loss risks.
  3. Are AMMs only for Ethereum?: No — they operate on multiple blockchains, including BNB Chain, Polygon, and Avalanche.

Other Glossary Terms

DeFi

DeFi, or decentralized finance, refers to blockchain-based apps that offer financial services without banks. It runs on smart contracts, giving users full control over their assets.

Blockchain trilemma

The blockchain trilemma is the challenge of achieving scalability, security, and decentralization at the same time. Learn why it matters — and how projects try to balance the trade-offs.

Crypto Address

A crypto address is a unique identifier used for sending and receiving cryptocurrency on blockchain networks. Linked to a wallet

Public Blockchain

A public blockchain is an open, decentralized network where anyone can participate, validate transactions, and view the ledger. Learn how it works, its benefits, and the challenges it faces in scalability and security.

Circulating Supply

Circulating supply is the number of crypto tokens actively available in the market. It impacts price, market cap, and scarcity, making it a key metric for investors. Bitcoin has ~19.5M BTC circulating, while Ethereum's supply fluctuates.

Block in a blockchain

A block in a blockchain is a digital record that contains a batch of verified transactions, along with metadata such as a timestamp, cryptographic hash, and a reference to the previous block.