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Documentation Index

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Fee vaults are predeploy contracts on OP Stack L2 chains that collect and hold the different components of transaction fees. Unlike Ethereum where the base fee is burned, OP Stack chains route all fees into dedicated vault contracts, allowing chain operators to withdraw and manage collected revenue.

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Overview

Every OP Stack chain has four fee vaults, each collecting a specific fee component:
VaultAddressCollectsIntroduced
SequencerFeeVault0x4200000000000000000000000000000000000011Priority fees (tips)Legacy
BaseFeeVault0x4200000000000000000000000000000000000019Base fees (not burned on L2)Bedrock
L1FeeVault0x420000000000000000000000000000000000001AL1 data feesBedrock
OperatorFeeVault0x420000000000000000000000000000000000001BOperator feesIsthmus

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How fees flow into vaults

When a transaction is executed on an OP Stack chain, the total fee is split across vaults:
  • Base fee (gasUsed × baseFee) goes to the BaseFeeVault
  • Priority fee (gasUsed × priorityFee) goes to the SequencerFeeVault
  • L1 data fee goes to the L1FeeVault
  • Operator fee (operatorFeeScalar × gasUsed + operatorFeeConstant) goes to the OperatorFeeVault
Each component has its own formula. For the full breakdown, see Transaction fees.

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Vault configuration

Each fee vault has three configurable parameters:
ParameterDescription
recipientThe address that receives withdrawn funds
minWithdrawalAmountMinimum ETH balance required before a withdrawal can be triggered
withdrawalNetworkWhether funds are withdrawn to an L1 or L2 address

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Withdrawal network

The withdrawalNetwork parameter determines how funds are routed when withdrawn:
  • L1 (0): Funds are sent to the recipient on L1 via the L2ToL1MessagePasser. This initiates a standard L2-to-L1 withdrawal that must be proven and finalized on L1.
  • L2 (1): Funds are sent directly to the recipient on L2 via a simple ETH transfer.

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Withdrawal mechanism

Fee vault withdrawals are permissionless — anyone can trigger a withdrawal by calling the withdraw() function on any vault. This design ensures that collected fees can always be moved to the configured recipient without relying on a specific operator.

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How withdrawals work

  1. The caller invokes withdraw() on the vault contract.
  2. The vault checks that its balance meets the minWithdrawalAmount threshold.
  3. The entire vault balance is withdrawn (not a partial amount).
  4. The totalProcessed counter is incremented.
  5. Funds are routed based on withdrawalNetwork:
    • L2: Direct ETH transfer to the recipient.
    • L1: A withdrawal is initiated through the L2ToL1MessagePasser with a 400,000 gas limit. The withdrawal must then be proven and finalized on L1.

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Next steps