Swap Execution

Slippage tolerance sets max acceptable price change — 0.5% for stablecoins, 1-3% for volatile pairs, higher for low liquidity tokens
"Price impact" and "slippage" are different — impact is immediate effect of your trade size, slippage is protection against price movement
High price impact (>2%) means you're moving the market — split large trades or use limit orders on Uniswap X
Transaction deadline prevents stale swaps — 20-30 minutes default is usually fine, but pending tx beyond deadline will fail

MEV and Frontrunning

Public swaps on Uniswap are visible in mempool before execution — bots can sandwich your trade
Use MEV protection: swap through Uniswap wallet (built-in protection), or connect via Flashbots Protect RPC
Signs of sandwich: execution price worse than quoted, with suspicious buy before and sell after your tx
Uniswap X routes through private order flow — significantly reduces MEV extraction

First swap of any token requires approval transaction — this is normal, costs gas, and happens once per token per spender
"Infinite approval" is the default — convenient but risky if Uniswap router is ever compromised
Check and revoke old approvals at revoke.cash — approvals persist forever until explicitly revoked
Approval transaction can succeed while swap fails — user pays gas for approval but swap reverts on slippage