# Swap Fees

Swap fees come in two different forms for v3 pools:

• Static Swap Fee:
  • Initially set as part of the pool registration.
  • Authorized addresses can then change the value by invoking the vault.setStaticSwapFeePercentage(address pool, uint256 swapFeePercentage) function.
  • If the staticSwapFeePercentage is changed, it will emit an event: SwapFeePercentageChanged(pool, swapFeePercentage);
  • setStaticSwapFeePercentage can also be called as part of a regular hook
• Dynamic Swap Fee:
  • At registration pools can be set up to use dynamic swap fees.
  • The Vault uses the _getSwapFeePercentage(PoolConfig memory config) to fetch the swap fee from the pool. This function can implement arbitrary logic.
  • Even when a pool is set to use dynamic swap fees, it still maintains a static swap fee. However, this static fee is not utilized.

The pseudo logic to determine how swap fee is calculated looks like:

swapFeePercentage =
     Pool has DynamicSwapFee => call DynamicSwapFeeHook in the pool
     else => load static Swap fee percentage from Vault