Uniswap V4 🦄

Swap tokens and read pool state on Uniswap V4 via the Universal Router.

Chains: Base (8453), Ethereum (1), Base Sepolia (84532)

Addresses from docs.uniswap.org/contracts/v4/deployments, verified 2026-02-08.

Decision Tree

1. Read pool state? → src/pool-info.ts (free, no gas, no key)
2. Get swap quote? → src/quote.ts (free, uses on-chain V4Quoter)
3. Approve tokens? → src/approve.ts (write, ~100K gas, needs PRIVATE_KEY)
4. Execute swap? → src/swap.ts (write, ~300-350K gas, needs PRIVATE_KEY)
5. First time with an ERC20? → Run approve first, or use --auto-approve on swap

Scripts Reference

All scripts in src/. Run with npx tsx. Pass --help for usage.

pool-info.ts — Read Pool State (free)

Returns pool ID, sqrtPriceX96, tick, liquidity, fees, token symbols/decimals. Auto-detects the best pool by liquidity (or specify --fee/--tick-spacing).

npx tsx src/pool-info.ts --token0 ETH --token1 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 --chain base --rpc $BASE_RPC_URL

Env: BASE_RPC_URL or ETH_RPC_URL (or pass --rpc)

quote.ts — Quote Swap Amounts (free)

Quotes exact input amounts via the on-chain V4Quoter contract (simulation, no tx). Returns expected output amount and gas estimate.

npx tsx src/quote.ts \
  --token-in ETH \
  --token-out 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 \
  --amount 10000000000000000 \
  --chain base \
  --rpc $BASE_RPC_URL

Env: BASE_RPC_URL or ETH_RPC_URL

approve.ts — Set Up Token Approvals (write)

Two-step Permit2 flow: ERC20 → Permit2, then Permit2 → Universal Router. Skips if already approved. Only needed for ERC20 tokens (not ETH).

PRIVATE_KEY=0x... npx tsx src/approve.ts \
  --token 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 \
  --chain base \
  --rpc $BASE_RPC_URL \
  --json

Env: PRIVATE_KEY (required), BASE_RPC_URL

swap.ts — Execute Swap (write)

Exact-input swap via Universal Router. Quotes expected output first, applies slippage, then sends the transaction.