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Using the Optimism SDK

This tutorial will walk you through the process of using the Optimism SDK (opens in a new tab) to interact with your OP Stack chain. The Optimism SDK natively supports various OP Chains including OP Mainnet and Base. To check whether your OP Chain is already supported, see the Optimism SDK docs (opens in a new tab).

You will need to already have created your own OP Stack chain to follow this tutorial. Check out the tutorial on Creating Your Own L2 Rollup Testnet if you haven't done so already.

Dependencies

Find Contract Addresses

You will need to find the addresses for a number of smart contracts that are part of your OP Stack chain in order to use the Optimism SDK. If you followed the instructions in the Creating Your Own L2 Rollup Testnet tutorial, you can find the addresses by looking at the JSON artifacts within the directory optimism/packages/contracts-bedrock/deployments/getting-started.

Simply run the following command from inside the directory optimism/packages/contracts-bedrock to print the list of addresses you'll need:

./scripts/print-addresses.sh getting-started --sdk

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Make sure you have jq (opens in a new tab) installed when running this command.

You should see output similar to the following:

AddressManager: 0x...
L1CrossDomainMessengerProxy: 0x...
L1StandardBridgeProxy: 0x...
L2OutputOracleProxy: 0x...
OptimismPortalProxy: 0x...

Save these addresses somewhere so you can use them in the next section.

Create a Demo Project

You're going to use the Optimism SDK for this tutorial. Since the Optimism SDK is a Node.js (opens in a new tab) library, you'll need to create a Node.js project to use it.

Make a Project Folder

mkdir op-sdk-sample-project
cd op-sdk-sample-project

Initialize the Project

pnpm init

Install the Optimism SDK

pnpm add @eth-optimism/sdk

Install ethers.js

pnpm add ethers@^5

Start the Node REPL

You're going to use the Node REPL to interact with the Optimism SDK. To start the Node REPL run the following command in your terminal:

node

This will bring up a Node REPL prompt that allows you to run javascript code.

Import Dependencies

You need to import some dependencies into your Node REPL session.

Import the Optimism SDK

const optimism = require("@eth-optimism/sdk")

Import ethers.js

const ethers = require("ethers")

Set Session Variables

You'll need a few variables throughout this tutorial. Let's set those up now.

Create the RPC providers

const l1Provider = new ethers.providers.StaticJsonRpcProvider("https://rpc.ankr.com/eth_sepolia")
const l2Provider = new ethers.providers.StaticJsonRpcProvider("https://sepolia.optimism.io")

Set the contract addresses

Using the addresses you accessed earlier, set the contract addresses in the following variables:

const AddressManager = '0x...'
const L1CrossDomainMessenger = '0x...'
const L1StandardBridge = '0x...' 
const OptimismPortal = '0x...'
const L2OutputOracle = '0x...'

Set the chain IDs

const l1ChainId = await l1Provider.getNetwork().then(network => network.chainId)
const l2ChainId = await l2Provider.getNetwork().then(network => network.chainId)

Initialize the Optimism SDK

You can now create an instance of the CrossChainMessenger object from the Optimism SDK. This will allow you to easily handle cross-domain messages between L1 and L2.

Simply create the object:

const messenger = new optimism.CrossChainMessenger({
  l1SignerOrProvider: l1Provider,
  l2SignerOrProvider: l2Provider,
  l1ChainId,
  l2ChainId,
 
  // This is the only part that differs from natively included chains.
  contracts: {
    l1: {
      AddressManager,
      L1CrossDomainMessenger,
      L1StandardBridge,
      OptimismPortal,
      L2OutputOracle,
 
      // Need to be set to zero for this version of the SDK.
      StateCommitmentChain: ethers.constants.AddressZero,
      CanonicalTransactionChain: ethers.constants.AddressZero,
      BondManager: ethers.constants.AddressZero,
    }
  }
})

Note that you've passed in the RPC providers you created earlier, the addresses of the smart contracts you deployed, and the chain ID of your OP Stack chain.

Next Steps

You can now use the SDK to interact with your OP Stack chain just like you would with other chains like OP Mainnet. See existing tutorials, like the tutorial on Bridging ETH With the Optimism SDK or Bridging ERC-20 Tokens With the Optimism SDK, for examples of how to use the Optimism SDK.

Creating Your Own L2 Rollup Testnet Adding Attributes to the Derivation Function