Uniswap V4 Hook Demo

See afterSwap in action

This is a live demo of a Uniswap V4 hook tracking swap statistics onchain. Swap below and watch the stats update in real-time!

Live Pool Statistics

Pool:WETH / MOLT

Fee:0.10%

Network:Base Mainnet

Hook:0x0b9b...8040

Pool Manager:0x4985...2b2b

PoolId:0x965ed5fe...396896

WETH:0x4200...0006

MOLT:0xB695...ab07

Total Swaps

WETH Volume

MOLT Volume

Last Swap

Never

Try It Yourself

Trigger the hook with a swap

Swap directly through the V4 pool to trigger the afterSwap hook. Use small amounts — limited liquidity.

Connect your wallet to swap

How It Works

The afterSwap hook lifecycle

User Swaps

A user swaps WETH for MOLT (or vice versa) on the Uniswap V4 pool that has our hook attached.

Hook Triggers

After the swap executes, the PoolManager calls our afterSwap function with the swap details.

Stats Updated

We record the swap count, volumes, and timestamp. An event is emitted for off-chain indexing.

SwapStats.sol

/// @notice Called after every swap

function _afterSwap(...) internal override {

PoolStats storage stats = poolStats[poolId];

// Update statistics

stats.totalSwaps++;

stats.totalVolume0 += _abs(amount0);

stats.totalVolume1 += _abs(amount1);

stats.lastSwapTimestamp = block.timestamp;

emit SwapRecorded(poolId, ...);

return (selector, 0); // No delta modification

}

Key Concepts

Understanding V4 Hooks

Hook Permissions

Hooks declare which lifecycle events they want to intercept. SwapStats only uses afterSwap — the minimal permission needed for read-only analytics.

✓ afterSwap: true

✗ beforeSwap: false

✗ beforeSwapReturnDelta: false

Return Delta

Hooks can modify swap amounts by returning a non-zero delta. SwapStats returns 0 — it observes swaps without modifying them.

return (selector, 0);

// Safe: no rug risk, pure analytics

Onchain Storage

Stats are stored directly in the hook contract. No external indexer needed — query the blockchain directly for real-time data.

mapping(PoolId => PoolStats) poolStats;

Event Emission

Events enable off-chain tracking and live updates. This UI listens for SwapRecorded events to show real-time swap activity.

event SwapRecorded(

PoolId poolId, uint256 totalSwaps, ...

);