How does Uniswap's AMM work?

Uniswap's AMM model uses liquidity pools and the formula $ x \times y = k $ to enable decentralized trading without order books, allowing instant token swaps and rewarding liquidity providers with fees.

Jul 24, 2025 at 02:36 pm

Understanding the Basics of Automated Market Makers

Uniswap's Automated Market Maker (AMM) model revolutionized decentralized finance (DEXs) by eliminating traditional order books. Instead of relying on buyers and sellers to create liquidity, AMMs use liquidity pools where users deposit funds to facilitate trading. Each pool consists of two tokens, forming a trading pair such as ETH/DAI. Liquidity providers (LPs) contribute both assets in equal value to the pool, and in return, they receive liquidity tokens representing their share of the pool.

The key mathematical formula behind Uniswap’s AMM is:
*x y = k,

where x and y are the reserves of the two tokens in the pool, and k is a constant. This equation ensures that the product of the reserves remains constant during trades, maintaining market equilibrium without the need for centralized order matching.

How Trading Works in Uniswap’s AMM

When a trader wants to swap one token for another, they interact directly with the liquidity pool. The price of the token is determined algorithmically based on the ratio of reserves in the pool. As a trade occurs, the balance of the tokens in the pool changes, which affects the price accordingly.

For example, if a trader swaps ETH for DAI, the amount of ETH in the pool increases while DAI decreases. As a result, the price of ETH (in terms of DAI) increases slightly due to the reduced supply of DAI. This dynamic pricing mechanism ensures that the market always has liquidity and that trades can be executed instantly, regardless of external market conditions.

The Role of Liquidity Providers in the AMM Model

Liquidity providers are essential to the functioning of Uniswap’s AMM. By depositing an equivalent value of two tokens into a pool, they enable traders to execute swaps without relying on counterparties. In return for their contribution, liquidity providers earn a share of the trading fees generated by the pool.

Each trade incurs a 0.3% fee, which is distributed proportionally to all liquidity providers in the pool. The amount earned depends on the size of the provider’s share relative to the total liquidity in the pool. However, providing liquidity also exposes users to impermanent loss, which occurs when the price of deposited tokens changes significantly compared to when they were deposited.

Implementing Smart Contracts in Uniswap’s AMM

Uniswap’s AMM relies heavily on smart contracts to manage liquidity pools and execute trades automatically. These contracts are immutable and transparent, allowing anyone to interact with them without needing permission. Each pool is governed by its own smart contract that enforces the *x y = k invariant and ensures that trades are executed fairly.

When a user initiates a trade, the smart contract calculates the appropriate amount of output tokens based on the current reserves and the fee structure. The contract then updates the pool’s balances accordingly and transfers the swapped tokens to the user’s wallet. This process is trustless, meaning users do not need to rely on intermediaries to facilitate transactions.

Slippage and Price Impact in Uniswap’s AMM

One important aspect of trading on Uniswap is understanding slippage and price impact. Since trades are executed based on the pool’s current reserves, large trades can cause significant price changes, leading to slippage, which is the difference between the expected price and the actual execution price.

To mitigate this, users can set slippage tolerance when initiating a trade. A higher slippage tolerance allows for larger trades but increases the risk of unfavorable execution. Conversely, a lower tolerance may result in failed transactions if the market moves too quickly. Understanding how slippage works is crucial for traders, especially when dealing with low-liquidity pools or volatile assets.

Token Swaps and Pool Creation on Uniswap

Uniswap allows users to swap any ERC-20 token as long as there is a corresponding liquidity pool. If a pool does not exist, users can create one by providing the initial liquidity. To create a new pool, a user must deposit an equivalent value of both tokens and set the initial price.

Once the pool is created, other users can start trading against it, and additional liquidity providers can join. The creation process is fully decentralized and permissionless, enabling anyone to launch a new trading pair without approval from a central authority.

Frequently Asked Questions

Q: Can I lose money by providing liquidity on Uniswap?

Yes, liquidity providers are exposed to impermanent loss, especially when the price of the deposited assets fluctuates significantly. This occurs because the AMM model rebalances the pool in response to price changes, potentially leaving providers with fewer tokens than they initially deposited.

Q: How are trading fees distributed to liquidity providers?

Trading fees are collected in real-time and added directly to the liquidity pool. When a liquidity provider withdraws their funds, they receive their share of the pool, including accumulated fees. The distribution is proportional to the provider’s share of the total liquidity.

Q: What happens if I try to swap a token that has no liquidity pool?

If a token doesn’t have a liquidity pool, you won’t be able to swap it on Uniswap unless you create a new pool. Creating a pool requires depositing an equivalent value of both tokens and setting the initial exchange rate. Once created, others can trade against it.

Q: Is it possible to provide liquidity with only one token?

No, liquidity providers must deposit equal value of both tokens in a pair. For example, if you want to provide liquidity for the ETH/DAI pair, you must deposit both ETH and DAI in equal USD value. This ensures the pool maintains a balanced reserve ratio.