Table of Contents
- Overview
- LegacyMessagePasser
- L2ToL1MessagePasser
- DeployerWhitelist
- LegacyERC20ETH
- WETH9
- L2CrossDomainMessenger
- L2StandardBridge
- L1BlockNumber
- GasPriceOracle
- L1Block
- ProxyAdmin
- SequencerFeeVault
- OptimismMintableERC20Factory
- OptimismMintableERC721Factory
- BaseFeeVault
- L1FeeVault
Predeployed smart contracts exist on Optimism at predetermined addresses in the genesis state. They are similar to precompiles but instead run directly in the EVM instead of running native code outside of the EVM.
Predeploys are used instead of precompiles to make it easier for multiclient implementations as well as allowing for more integration with hardhat/foundry network forking.
Predeploy addresses exist in 1 byte namespace 0x42000000000000000000000000000000000000xx.
Proxies are set at each possible predeploy address except for the
GovernanceToken and the ProxyAdmin.
The LegacyERC20ETH predeploy lives at a special address 0xDeadDeAddeAddEAddeadDEaDDEAdDeaDDeAD0000
and there is no proxy deployed at that account.
The following table includes each of the predeploys. The system version
indicates when the predeploy was introduced. The possible values are Legacy
or Bedrock. Deprecated contracts should not be used.
| Name | Address | Introduced | Deprecated | Proxied |
|---|---|---|---|---|
| LegacyMessagePasser | 0x4200000000000000000000000000000000000000 | Legacy | Yes | Yes |
| DeployerWhitelist | 0x4200000000000000000000000000000000000002 | Legacy | Yes | Yes |
| LegacyERC20ETH | 0xDeadDeAddeAddEAddeadDEaDDEAdDeaDDeAD0000 | Legacy | Yes | No |
| WETH9 | 0x4200000000000000000000000000000000000006 | Legacy | No | No |
| L2CrossDomainMessenger | 0x4200000000000000000000000000000000000007 | Legacy | No | Yes |
| L2StandardBridge | 0x4200000000000000000000000000000000000010 | Legacy | No | Yes |
| SequencerFeeVault | 0x4200000000000000000000000000000000000011 | Legacy | No | Yes |
| OptimismMintableERC20Factory | 0x4200000000000000000000000000000000000012 | Legacy | No | Yes |
| L1BlockNumber | 0x4200000000000000000000000000000000000013 | Legacy | Yes | Yes |
| GasPriceOracle | 0x420000000000000000000000000000000000000F | Legacy | No | Yes |
| GovernanceToken | 0x4200000000000000000000000000000000000042 | Legacy | No | No |
| L1Block | 0x4200000000000000000000000000000000000015 | Bedrock | No | Yes |
| L2ToL1MessagePasser | 0x4200000000000000000000000000000000000016 | Bedrock | No | Yes |
| L2ERC721Bridge | 0x4200000000000000000000000000000000000014 | Legacy | No | Yes |
| OptimismMintableERC721Factory | 0x4200000000000000000000000000000000000017 | Bedrock | No | Yes |
| ProxyAdmin | 0x4200000000000000000000000000000000000018 | Bedrock | No | Yes |
| BaseFeeVault | 0x4200000000000000000000000000000000000019 | Bedrock | No | Yes |
| L1FeeVault | 0x420000000000000000000000000000000000001a | Bedrock | No | Yes |
Address: 0x4200000000000000000000000000000000000000
The LegacyMessagePasser contract stores commitments to withdrawal
transactions before the Bedrock upgrade. A merkle proof to a particular
storage slot that commits to the withdrawal transaction is used as part
of the withdrawing transaction on L1. The expected account that includes
the storage slot is hardcoded into the L1 logic. After the bedrock upgrade,
the L2ToL1MessagePasser is used instead. Finalizing withdrawals from this
contract will no longer be supported after the Bedrock and is only left
to allow for alternative bridges that may depend on it. This contract does
not forward calls to the L2ToL1MessagePasser and calling it is considered
a no-op in context of doing withdrawals through the CrossDomainMessenger
system.
Any pending withdrawals that have not been finalized are migrated to the
L2ToL1MessagePasser as part of the upgrade so that they can still be
finalized.
Address: 0x4200000000000000000000000000000000000016
The L2ToL1MessagePasser stores commitments to withdrawal transactions.
When a user is submitting the withdrawing transaction on L1, they provide a
proof that the transaction that they withdrew on L2 is in the sentMessages
mapping of this contract.
Any withdrawn ETH accumulates into this contract on L2 and can be
permissionlessly removed from the L2 supply by calling the burn() function.
Address: 0x4200000000000000000000000000000000000002
The DeployerWhitelist is a predeploy that was used to provide additional safety
during the initial phases of Optimism.
It previously defined the accounts that are allowed to deploy contracts to the network.
Arbitrary contract deployment was subsequently enabled and it is not possible to turn
off. In the legacy system, this contract was hooked into CREATE and
CREATE2 to ensure that the deployer was allowlisted.
In the Bedrock system, this contract will no longer be used as part of the
CREATE codepath.
This contract is deprecated and its usage should be avoided.
Address: 0xDeadDeAddeAddEAddeadDEaDDEAdDeaDDeAD0000
The LegacyERC20ETH predeploy represents all ether in the system before the
Bedrock upgrade. All ETH was represented as an ERC20 token and users could opt
into the ERC20 interface or the native ETH interface.
The upgrade to Bedrock migrates all ether out of this contract and moves it to its native representation. All of the stateful methods in this contract will revert after the Bedrock upgrade.
This contract is deprecated and its usage should be avoided.
Address: 0x4200000000000000000000000000000000000006
WETH9 is the standard implementation of Wrapped Ether on Optimism. It is a
commonly used contract and is placed as a predeploy so that it is at a
deterministic address across Optimism based networks.
Address: 0x4200000000000000000000000000000000000007
The L2CrossDomainMessenger gives a higher level API for sending cross domain
messages compared to directly calling the L2ToL1MessagePasser.
It maintains a mapping of L1 messages that have been relayed to L2
to prevent replay attacks and also allows for replayability if the L1 to L2
transaction reverts on L2.
Any calls to the L1CrossDomainMessenger on L1 are serialized such that they
go through the L2CrossDomainMessenger on L2.
The relayMessage function executes a transaction from the remote domain while
the sendMessage function sends a transaction to be executed on the remote
domain through the remote domain's relayMessage function.
Address: 0x4200000000000000000000000000000000000010
The L2StandardBridge is a higher level API built on top of the
L2CrossDomainMessenger that gives a standard interface for sending ETH or
ERC20 tokens across domains.
To deposit a token from L1 to L2, the L1StandardBridge locks the token and
sends a cross domain message to the L2StandardBridge which then mints the
token to the specified account.
To withdraw a token from L2 to L1, the user will burn the token on L2 and the
L2StandardBridge will send a message to the L1StandardBridge which will
unlock the underlying token and transfer it to the specified account.
The OptimismMintableERC20Factory can be used to create an ERC20 token contract
on a remote domain that maps to an ERC20 token contract on the local domain
where tokens can be deposited to the remote domain. It deploys an
OptimismMintableERC20 which has the interface that works with the
StandardBridge.
This contract can also be deployed on L1 to allow for L2 native tokens to be withdrawn to L1.
Address: 0x4200000000000000000000000000000000000013
The L1BlockNumber returns the last known L1 block number. This contract was
introduced in the legacy system and should be backwards compatible by calling
out to the L1Block contract under the hood.
It is recommended to use the L1Block contract for getting information about
L1 on L2.
Address: 0x420000000000000000000000000000000000000F
In the legacy system, the GasPriceOracle was a permissioned contract
that was pushed the L1 basefee and the L2 gas price by an offchain actor.
The offchain actor observes the L1 blockheaders to get the
L1 basefee as well as the gas usage on L2 to compute what the L2 gas price
should be based on a congestion control algorithm.
After Bedrock, the GasPriceOracle is no longer a permissioned contract
and only exists to preserve the API for offchain gas estimation. The
function getL1Fee(bytes) accepts an unsigned RLP transaction and will return
the L1 portion of the fee. This fee pays for using L1 as a data availability
layer and should be added to the L2 portion of the fee, which pays for
execution, to compute the total transaction fee.
The values used to compute the L2 portion of the fee are:
- scalar
- overhead
- decimals
After the Bedrock upgrade, these values are instead managed by the
SystemConfig contract on L2. The scalar and overhead values
are sent to the L1Block contract each block and the decimals value
has been hardcoded to 6.
Address: 0x4200000000000000000000000000000000000015
The L1Block was introduced in Bedrock and is responsible for maintaining L1 context in L2. This allows for L1 state to be accessed in L2.
ProxyAdmin
Address: 0x4200000000000000000000000000000000000018
The ProxyAdmin is the owner of all of the proxy contracts set at the
predeploys. It is itself behind a proxy. The owner of the ProxyAdmin will
have the ability to upgrade any of the other predeploy contracts.
Address: 0x4200000000000000000000000000000000000011
The SequencerFeeVault accumulates any transaction priority fee and is the value of
block.coinbase.
When enough fees accumulate in this account, they can be withdrawn to an immutable L1 address.
To change the L1 address that fees are withdrawn to, the contract must be upgraded by changing its proxy's implementation key.
Address: 0x4200000000000000000000000000000000000012
The OptimismMintableERC20Factory is responsible for creating ERC20 contracts on L2 that can be
used for depositing native L1 tokens into. These ERC20 contracts can be created permisionlessly
and implement the interface required by the StandardBridge to just work with deposits and withdrawals.
Each ERC20 contract that is created by the OptimismMintableERC20Factory allows for the L2StandardBridge to mint
and burn tokens, depending on if the user is depositing from L1 to L2 or withdrawaing from L2 to L1.
Address: 0x4200000000000000000000000000000000000017
The OptimismMintableERC721Factory is responsible for creating ERC721 contracts on L2 that can be used for
depositing native L1 NFTs into.
Address: 0x4200000000000000000000000000000000000019
The BaseFeeVault predeploy receives the basefees on L2. The basefee is not
burnt on L2 like it is on L1. Once the contract has received a certain amount
of fees, the ETH can be withdrawn to an immutable address on
L1.
Address: 0x420000000000000000000000000000000000001a
The L1FeeVault predeploy receives the L1 portion of the transaction fees.
Once the contract has received a certain amount of fees, the ETH can be
withdrawn to an immutable address on L1.