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After you have spun up your sequencer, you need to configure a batcher to submit L2 transaction batches to L1.
Step 3 of 5: This tutorial is designed to be followed step-by-step. Each step builds on the previous one.
Automated Setup AvailableFor a complete working setup with all components, check out the automated approach in the code directory.

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Understanding the batcher’s role

The batcher (op-batcher) serves as a crucial component that bridges your L2 chain data to L1. Its primary responsibilities include:
  • Batch submission: Collecting L2 transactions and submitting them as batches to L1
  • Data availability: Ensuring L2 transaction data is available on L1 for verification
  • Cost optimization: Compressing and efficiently packing transaction data to minimize L1 costs
  • Channel management: Managing data channels for optimal batch submission timing
The batcher reads transaction data from your sequencer and submits compressed batches to the BatchInbox contract on L1.

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Prerequisites

Before setting up your batcher, ensure you have: Running infrastructure:
  • An operational sequencer node
  • Access to a L1 RPC endpoint
Network information:
  • Your L2 chain ID and network configuration
  • L1 network details (chain ID, RPC endpoints)
  • BatchInbox contract address from your deployment
For setting up the batcher, we recommend using Docker as it provides a consistent and isolated environment. Building from source is also available for more advanced users.
  • Use docker
  • Build from source
If you prefer containerized deployment, you can use the official Docker images and do the following:
1

Set up directory structure and copy configuration files

# Create your batcher directory inside rollup
cd ../    # Go back to rollup directory if you're in sequencer
mkdir batcher
cd batcher

# Copy configuration files from deployer
cp ../deployer/.deployer/state.json .

# Extract the BatchInbox address
BATCH_INBOX_ADDRESS=$(cat state.json | jq -r '.opChainDeployments[0].systemConfigProxyAddress')
echo "BatchInbox Address: $BATCH_INBOX_ADDRESS"
2

Create environment variables file

OP Stack Standard VariablesThe batcher uses OP Stack standard environment variables following the OP Stack conventions. These are prefixed with OP_BATCHER_ for batcher-specific settings.
# Create .env file with your actual values
cat > .env << 'EOF'
# L1 Configuration - Replace with your actual RPC URLs
OP_BATCHER_L1_RPC_URL=https://sepolia.infura.io/v3/YOUR_ACTUAL_INFURA_KEY
# Private key - Replace with your actual private key
OP_BATCHER_PRIVATE_KEY=YOUR_ACTUAL_PRIVATE_KEY

# L2 Configuration - Should match your sequencer setup
OP_BATCHER_L2_ETH_RPC=http://op-geth:8545
OP_BATCHER_ROLLUP_RPC=http://op-node:8547

# Contract addresses - Extract from your op-deployer output
OP_BATCHER_BATCH_INBOX_ADDR=YOUR_ACTUAL_BATCH_INBOX_ADDRESS

# Batcher configuration
OP_BATCHER_POLL_INTERVAL=1s
OP_BATCHER_SUB_SAFETY_MARGIN=6
OP_BATCHER_NUM_CONFIRMATIONS=1
OP_BATCHER_SAFE_ABORT_NONCE_TOO_LOW_COUNT=3
OP_BATCHER_MAX_CHANNEL_DURATION=1
OP_BATCHER_DATA_AVAILABILITY_TYPE=calldata

# RPC configuration
OP_BATCHER_RPC_PORT=8548
EOF
Important: Replace ALL placeholder values (YOUR_ACTUAL_*) with your real configuration values.
3

Create a docker-compose.yml file

This configuration assumes your sequencer is running in a Docker container named sequencer-node on the same op-stack network. Make sure your sequencer is running before starting the batcher.

services:
  op-batcher:
    image: us-docker.pkg.dev/oplabs-tools-artifacts/images/op-batcher:v1.13.2
    volumes:
      - .:/workspace
    working_dir: /workspace
    ports:
      - "8548:8548"
    env_file:
      - .env
    networks:
      - sequencer-node_default
    command: >
      op-batcher
      --rpc.addr=0.0.0.0
      --rpc.enable-admin
      --resubmission-timeout=30s
      --log.level=info
      --log.format=json
    restart: unless-stopped

networks:
  sequencer-node_default:
    external: false
4

Start the batcher service

# Make sure your sequencer network exists
# Start the batcher
docker-compose up -d

# View logs
docker-compose logs -f op-batcher
5

Verify batcher is running

# Check container status
docker-compose ps
6

Final directory structure

rollup/
├── deployer/            # From previous step
│   └── .deployer/      # Contains genesis.json and rollup.json
├── sequencer/          # From previous step
└── batcher/           # You are here
    ├── state.json     # Copied from deployer
    ├── .env           # Environment variables
    └── docker-compose.yml # Docker configuration
Your batcher is now operational and will continuously submit L2 transaction batches to L1!
Understanding common startup messagesWhen starting your batcher, you might see various log messages:
  • Added L2 block to local state: Normal operation, shows the batcher processing blocks
  • SetMaxDASize RPC method unavailable: Expected if the op-geth version used doesn’t support this method.
  • context canceled errors during shutdown: Normal cleanup messages
  • Failed to query L1 tip: Can occur during graceful shutdowns
Most of these messages are part of normal operation. For detailed explanations of configuration options and troubleshooting, see the Batcher configuration reference.

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What’s Next?

Excellent! Your batcher is publishing transaction data to L1. The next step is to set up the proposer to submit state root proposals.

Spin up proposer →

Next: Configure and start op-proposer to submit L2 state roots to L1 for withdrawal verification.

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