UniswapV4Hook
EthereumRegisteredA buy/sell hook deducting a 4% fee per swap: ETH fees from buys accumulate in a burn pot for buyback-and-burn via the pool; token fees from sells queue for burning. Pool init and liquidity addition are one-time per token; exact-output swaps always revert. Sells can be gated by an admin allowlist (timeBased/hasValue): any address can activate the restriction per token via pitchWC(), after which only deployer-allowlisted addresses can sell, and only the deployer can deactivate it.
What it can do
Its code executes inside each trade in pools that use it.
It can take or add tokens during a swap. Fees, burns and custom curves work this way, and so do scams.
It checks every deposit before it goes in.
It runs when a pool is created, often to lock in that pool’s settings.