> ## Documentation Index
> Fetch the complete documentation index at: https://docs.abs.xyz/llms.txt
> Use this file to discover all available pages before exploring further.

# List of System Contracts

> Explore all of the system contracts that Abstract implements.

## AccountCodeStorage

The `AccountCodeStorage` contract is responsible for storing the code hashes of accounts for retrieval
whenever the VM accesses an `address`.

The address is looked up in the `AccountCodeStorage` contract, if the associated value is non-zero (i.e. the address has code stored), this code hash
is used by the VM for the account.

**Contract Address:** `0x0000000000000000000000000000000000008002`

<Card title="View the source code for AccountCodeStorage" href="https://github.com/matter-labs/era-contracts/tree/main/system-contracts/contracts/AccountCodeStorage.sol" icon="github">
  View the AccountCodeStorage source code on Github.
</Card>

## BootloaderUtilities

Learn more about the bootloader and this system contract in the
[bootloader](/how-abstract-works/system-contracts/bootloader) section.

**Contract Address:** `0x000000000000000000000000000000000000800c`

<Card title="View the source code for BootloaderUtilities" href="https://github.com/matter-labs/era-contracts/tree/main/system-contracts/contracts/BootloaderUtilities.sol" icon="github">
  View the BootloaderUtilities source code on Github.
</Card>

## ComplexUpgrader

This contract is used to perform complex multi-step upgrades on the L2.
It contains a single function, `upgrade`, which executes an upgrade of the L2
by delegating calls to another contract.

**Contract Address:** `0x000000000000000000000000000000000000800f`

<Card title="View the source code for ComplexUpgrader" href="https://github.com/matter-labs/era-contracts/tree/main/system-contracts/contracts/ComplexUpgrader.sol" icon="github">
  View the ComplexUpgrader source code on Github.
</Card>

## Compressor

This contract is used to compress the data that is published to the L1, specifically, it:

* Compresses the deployed smart contract bytecodes.
* Compresses the state diffs (and validates state diff compression).

**Contract Address:** `0x000000000000000000000000000000000000800e`

<Card title="View the source code for Compressor" href="https://github.com/matter-labs/era-contracts/tree/main/system-contracts/contracts/Compressor.sol" icon="github">
  View the Compressor source code on Github.
</Card>

## Constants

This contract contains helpful constant values that are used throughout the system
and can be used in your own smart contracts. It includes:

* Addresses for all system contracts.
* Values for other system constants such as `MAX_NUMBER_OF_BLOBS`, `CREATE2_PREFIX`, etc.

<Card title="View the source code for Constants" href="https://github.com/matter-labs/era-contracts/tree/main/system-contracts/contracts/Constants.sol" icon="github">
  View the Constants source code on Github.
</Card>

## ContractDeployer

This contract is responsible for deploying smart contracts on Abstract as well as
generating the address of the deployed contract.
Before deployment, it ensures the code hash of the smart contract is known using the
[KnownCodesStorage](#knowncodesstorage) system contract.

See the [contract deployment](/how-abstract-works/evm-differences/contract-deployment) section
for more details.

**Contract Address:** `0x0000000000000000000000000000000000008006`

<Card title="View the source code for ContractDeployer" href="https://github.com/matter-labs/era-contracts/tree/main/system-contracts/contracts/ContractDeployer.sol" icon="github">
  View the ContractDeployer source code on Github.
</Card>

## Create2Factory

This contract can be used for deterministic contract deployment, i.e.
deploying a smart contract with the ability to predict the address of the deployed contract.

It contains two functions, `create2` and `create2Account`, which both
call a third function, `_relayCall` that relays the calldata to the
[ContractDeployer](#contractdeployer) contract.

You do not need to use this system contract directly, instead use [ContractDeployer](#contractdeployer).

**Contract Address:** `0x0000000000000000000000000000000000010000`

<Card title="View the source code for Create2Factory" href="https://github.com/matter-labs/era-contracts/tree/main/system-contracts/contracts/Create2Factory.sol" icon="github">
  View the Create2Factory source code on Github.
</Card>

## DefaultAccount

This contract is built to simulate the behavior of an EOA (Externally Owned Account) on the L2.
It is intended to act the same as an EOA would on Ethereum, enabling Abstract to support EOA wallets,
despite all accounts on Abstract being smart contracts.

As outlined in the [transaction flow](/how-abstract-works/native-account-abstraction/transaction-flow) section,
the `DefaultAccount` contract is used when the sender of a transaction is looked up and
no code is found for the address; indicating that the address of the sender is an EOA as opposed to
a [smart contract wallet](/how-abstract-works/native-account-abstraction/smart-contract-wallets).

<Card title="View the source code for DefaultAccount" href="https://github.com/matter-labs/era-contracts/tree/main/system-contracts/contracts/DefaultAccount.sol" icon="github">
  View the DefaultAccount source code on Github.
</Card>

## EmptyContract

Some contracts need no other code other than to return a success value.
An example of such an address is the `0` address. In addition, the
[bootloader](/how-abstract-works/system-contracts/bootloader) also needs to be
callable so that users can transfer ETH to it.

For these contracts, the EmptyContract code is inserted upon <Tooltip tip="The first block of the blockchain">Genesis</Tooltip>.
It is essentially a noop code, which does nothing and returns `success=1`.

**Contract Address:** `0x0000000000000000000000000000000000000000`

<Card title="View the source code for EmptyContract" href="https://github.com/matter-labs/era-contracts/tree/main/system-contracts/contracts/EmptyContract.sol" icon="github">
  View the EmptyContract source code on Github.
</Card>

## EventWriter

This contract is responsible for [emitting events](https://docs.soliditylang.org/en/latest/contracts.html#events).
It is not required to interact with this smart contract, the
standard Solidity `emit` keyword can be used.

**Contract Address:** `0x000000000000000000000000000000000000800d`

<Card title="View the source code for EventWriter" href="https://github.com/matter-labs/era-contracts/tree/main/system-contracts/contracts/EventWriter.yul" icon="github">
  View the EventWriter source code on Github.
</Card>

## ImmutableSimulator

This contract simulates the behavior of immutable variables in Solidity. It exists so that
smart contracts with the same Solidity code but different constructor parameters have the same bytecode.

It is not required to interact with this smart contract directly,
as it is used via the compiler.

**Contract Address:** `0x0000000000000000000000000000000000008005`

<Card title="View the source code for ImmutableSimulator" href="https://github.com/matter-labs/era-contracts/tree/main/system-contracts/contracts/ImmutableSimulator.sol" icon="github">
  View the ImmutableSimulator source code on Github.
</Card>

## KnownCodesStorage

Since Abstract stores the code hashes of smart contracts and not the code itself
(see [contract deployment](/how-abstract-works/evm-differences/contract-deployment)), the system must ensure that
it knows and stores the code hash of all smart contracts that are deployed.

The [ContractDeployer](#contractdeployer) checks this `KnownCodesStorage` contract to see if the
code hash of a smart contract is known before deploying it. If it is not known,
the contract will not be deployed and revert with an error `The code hash is not known`.

<Accordion title={`Why am I getting "the code hash is not known" error?`}>
  Likely, you are trying to deploy a smart contract without using the
  [ContractDeployer](#contractdeployer) system contract.

  See the [contract deployment section](/how-abstract-works/evm-differences/contract-deployment) for more details.
</Accordion>

**Contract Address:** `0x0000000000000000000000000000000000008004`

<Card title="View the source code for KnownCodesStorage" href="https://github.com/matter-labs/era-contracts/tree/main/system-contracts/contracts/KnownCodesStorage.sol" icon="github">
  View the KnownCodesStorage source code on Github.
</Card>

## L1Messenger

This contract is used for sending messages from Abstract to Ethereum.
It is used by the [KnownCodesStorage](#knowncodesstorage) contract to publish the
code hash of smart contracts to Ethereum.

Learn more about what data is sent in the [contract deployment section](/how-abstract-works/evm-differences/contract-deployment) section.

**Contract Address:** `0x0000000000000000000000000000000000008008`

<Card title="View the source code for L1Messenger" href="https://github.com/matter-labs/era-contracts/tree/main/system-contracts/contracts/L1Messenger.sol" icon="github">
  View the L1Messenger source code on Github.
</Card>

## L2BaseToken

This contract holds the balances of ETH for all accounts on the L2 and updates them
whenever other system contracts such as the [Bootloader](/how-abstract-works/system-contracts/bootloader),
[ContractDeployer](#contractdeployer), or [MsgValueSimulator](#msgvaluesimulator) perform
balance changes while simulating the `msg.value` behavior of Ethereum.

This is because the L2 does not have a set "native" token unlike Ethereum,
so functions such as `transferFromTo`, `balanceOf`, `mint`, `withdraw`, etc. are
implemented in this contract as if it were an ERC-20.

**Contract Address:** `0x000000000000000000000000000000000000800a`

<Card title="View the source code for L2BaseToken" href="https://github.com/matter-labs/era-contracts/tree/main/system-contracts/contracts/L2BaseToken.sol" icon="github">
  View the L2BaseToken source code on Github.
</Card>

## MsgValueSimulator

This contract calls the [L2BaseToken](#l2basetoken) contract’s `transferFromTo` function to
simulate the `msg.value` behavior of Ethereum.

**Contract Address:** `0x0000000000000000000000000000000000008009`

<Card title="View the source code for MsgValueSimulator" href="https://github.com/matter-labs/era-contracts/tree/main/system-contracts/contracts/MsgValueSimulator.sol" icon="github">
  View the MsgValueSimulator source code on Github.
</Card>

## NonceHolder

This contract stores the nonce for each account on the L2. More specifically, it stores both
the deployment nonce for each account and the transaction nonce for each account.

Before each transaction starts, the bootloader uses the `NonceHolder` to ensure
that the provided nonce for the transaction has not already been used by the sender.

During the [transaction validation](/how-abstract-works/native-account-abstraction/handling-nonces#considering-nonces-in-your-smart-contract-account),
it also enforces that the nonce *is* set as used before the transaction execution begins.

See more details in the [nonces](/how-abstract-works/evm-differences/nonces) section.

**Contract Address:** `0x0000000000000000000000000000000000008003`

<Card title="View the source code for NonceHolder" href="https://github.com/matter-labs/era-contracts/tree/main/system-contracts/contracts/NonceHolder.sol" icon="github">
  View the NonceHolder source code on Github.
</Card>

## PubdataChunkPublisher

This contract is responsible for creating [EIP-4844 blobs](https://www.eip4844.com/) and
publishing them to Ethereum. Learn more in the
[transaction lifecycle](/how-abstract-works/architecture/transaction-lifecycle) section.

**Contract Address:** `0x0000000000000000000000000000000000008011`

<Card title="View the source code for PubdataChunkPublisher" href="https://github.com/matter-labs/era-contracts/tree/main/system-contracts/contracts/PubdataChunkPublisher.sol" icon="github">
  View the PubdataChunkPublisher source code on Github.
</Card>

## SystemContext

This contract is used to store and provide various system parameters not included in the VM by default,
such as block-scoped, transaction-scoped, or system-wide parameters.

For example, variables such as `chainId`, `gasPrice`, `baseFee`, as well as system functions
such as `setL2Block` and `setNewBatch` are stored in this contract.

**Contract Address:** `0x000000000000000000000000000000000000800b`

<Card title="View the source code for SystemContext" href="https://github.com/matter-labs/era-contracts/tree/main/system-contracts/contracts/SystemContext.sol" icon="github">
  View the SystemContext source code on Github.
</Card>