What is a liquidity pool?

How do you swap a token when there’s nobody on the other side selling at that exact moment? On many decentralized exchanges (DEXs), you trade with a pool instead of a specific seller.

Think of an automated exchange booth with two containers, one for token A and one for token B. You put in A and take out B. The reserves change, and an algorithm calculates how many tokens you’ll receive. This mechanism is called an automated market maker (AMM). In practice, the “containers” are funds managed by a smart contract under predefined rules.

The funds are deposited by liquidity providers. In a typical two-token pool, they supply both assets according to its rules. In return, they’re usually entitled to a share of the swap fees. How you participate and how revenue is shared vary by protocol.

Why it matters

Liquidity pools let many decentralized finance (DeFi) apps work without a classic order book of buy and sell orders. When you make a swap, the available liquidity affects your execution price. When your trade is large relative to the available reserves, it can noticeably move the price against you.

We distinguish two different roles: using a pool to swap is one thing; putting your own funds into it is another. In the second case, you take on extra risks to share in the potential rewards.

What to watch out for

The typical risk for a provider is impermanent loss: the value of their position may be lower than it would have been if they had simply held the same tokens in their wallet. Fees aren’t guaranteed to cover that gap. Despite the name, the loss can become permanent when you withdraw.

There are also risks from contract bugs, malicious tokens or large providers suddenly pulling their liquidity. A pool can be created without any real vetting of the tokens it holds. A coin being in a pool isn’t a certificate of trustworthiness, and the yields shown aren’t guaranteed interest.