Flashbots tutorial & Flashbots bundles guide

What is Flashbots?

Flashbots is a research and development organization working on MEV infrastructure. Its documentation separates user transaction protection from searcher bundle submission to block builders.

The documented bundle path provides these capabilities:

• Ordered transaction groups for a target block
• Explicit timestamp, expiry, and revert handling
• Simulation before submission
• Optional distribution to selected builders
• On-chain verification of component transactions

Step-by-Step Guide

Bundle Structure

A Flashbots bundle consists of:

• Transactions: Ordered signed transactions with explicit revert policy
• Block Number: Target block for inclusion
• Min Timestamp: Minimum block timestamp (optional)
• Max Timestamp: Maximum block timestamp (optional)

Example Bundle

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "eth_sendBundle",
  "params": [{
    "txs": [
      "0x02f8...", // Transaction 1
      "0x02f8..."  // Transaction 2
    ],
    "blockNumber": "0x1234567",
    "minTimestamp": null,
    "maxTimestamp": null
  }]
}

Cost and Builder Payment Policy

Pricing and builder payment must be bounded and measured. Key considerations:

• Set a maximum total cost before submission
• Include expired and rejected attempts in the ledger
• Use the same workload when comparing builder configurations
• Use tools like our Gas Calculator to document a cost ceiling
• Re-simulate when state, target block, or fee assumptions change

Code Examples

JavaScript/TypeScript Example

import { ethers } from 'ethers';

const flashbotsRpc = 'https://rpc.flashbots.net';
const provider = new ethers.JsonRpcProvider(flashbotsRpc);

async function submitBundle(txs: string[], targetBlock: number) {
  const bundle = {
    jsonrpc: '2.0',
    id: 1,
    method: 'eth_sendBundle',
    params: [{
      txs: txs,
      blockNumber: '0x' + targetBlock.toString(16),
    }],
  };

  const response = await fetch(flashbotsRpc, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify(bundle),
  });

  return await response.json();
}

Python Example

import requests
import json

def submit_bundle(txs, target_block):
    url = 'https://rpc.flashbots.net'
    payload = {
        'jsonrpc': '2.0',
        'id': 1,
        'method': 'eth_sendBundle',
        'params': [{
            'txs': txs,
            'blockNumber': hex(target_block),
        }],
    }

    response = requests.post(url, json=payload)
    return response.json()

Best Practices

• Start Small: Test with small amounts before scaling up
• Monitor Status: Use Flashbots dashboard to track bundle status
• Optimize Gas: Refine fee policy only from complete, timestamped samples
• Error Handling: Implement robust error handling for failed submissions
• Rate Limiting: Respect rate limits to avoid being blocked
• Simulation: Use Flashbots simulation endpoint to test bundles before submission

Flashbots vs Public Mempool

Learn more in our Flashbots vs Public Mempool comparison.

Additional Resources

• Flashbots Documentation
• Flashbots Protect - User transaction protection route
• MEV Strategies Guide - Advanced strategies
• Ethereum MEV Guide - Network-specific tips
• Gas Calculator - Optimize gas prices

Next Steps

Ready to start using Flashbots? Here's what to do next:

1. Review the official Flashbots documentation
2. Set up your development environment
3. Test bundle submission in simulation mode
4. Start with small test bundles
5. Monitor and optimize your strategies
6. Consider using FRB Agent for automated MEV trading