How to Scan Ethereum Blocks and Extract Transaction Data

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Ethereum, as one of the most widely used blockchain platforms, generates vast amounts of on-chain data every second. For developers, analysts, and blockchain enthusiasts, being able to scan Ethereum blocks and extract transaction records is a fundamental skill. This guide walks you through the process of connecting to the Ethereum network, retrieving block data, parsing transactions, and identifying sender addresses—all using Go and the go-ethereum library.

Whether you're building a block explorer, analyzing transaction patterns, or auditing smart contracts, understanding how to programmatically access Ethereum's blockchain data is essential. We’ll cover everything from initializing a client to extracting complete transaction details—including the elusive from address.

Initializing an Ethereum Client in Go

The first step in interacting with the Ethereum blockchain is establishing a connection to a node. The go-ethereum library provides the tools needed to do this seamlessly in Go.

Begin by importing the ethclient package:

import "github.com/ethereum/go-ethereum/ethclient"

Then, use the Dial function to connect to an Ethereum node. You can connect to a public node such as those provided by Infura:

client, err := ethclient.Dial("https://mainnet.infura.io/v3/YOUR_INFURA_PROJECT_ID")
🔍 Note: Replace YOUR_INFURA_PROJECT_ID with your actual Infura API key for production use. For testing, you may use limited public endpoints, but expect throttling.

Here’s a complete example that connects to the Ethereum mainnet:

package main

import (
 "context"
 "fmt"
 "log"
 "github.com/ethereum/go-ethereum/ethclient"
)

func main() {
 client, err := ethclient.Dial("https://mainnet.infura.io/v3/YOUR_INFURA_PROJECT_ID")
 if err != nil {
  log.Fatal(err)
 }
 fmt.Println("Successfully connected to Ethereum network")
}

👉 Learn how to securely manage API keys and scale blockchain queries efficiently.

Fetching the Latest Block Number

Once connected, you can retrieve the latest block number to understand the current chain height. This is done using the HeaderByNumber method:

header, err := client.HeaderByNumber(context.Background(), nil)
if err != nil {
 log.Fatal(err)
}
fmt.Println("Latest block number:", header.Number.String())

This value represents the most recent block mined on the Ethereum blockchain and serves as a starting point for scanning historical data.

Retrieving a Specific Block

To analyze transaction data, you need to fetch a full block using its number. The BlockByNumber method returns a *types.Block, which contains metadata and all transactions within that block.

blockNumber := big.NewInt(5671744)
block, err := client.BlockByNumber(context.Background(), blockNumber)
if err != nil {
 log.Fatal(err)
}

fmt.Println("Block Number:", block.Number().Uint64())
fmt.Println("Timestamp:", block.Time().Uint64())
fmt.Println("Hash:", block.Hash().Hex())
fmt.Println("Difficulty:", block.Difficulty().Uint64())
fmt.Println("Total Transactions:", len(block.Transactions()))

This output gives you a comprehensive view of the block’s properties—ideal for monitoring network activity or debugging decentralized applications.

Extracting Transaction Details

Each block contains multiple transactions. You can iterate over them using the Transactions() method:

for _, tx := range block.Transactions() {
 fmt.Println("Tx Hash:", tx.Hash().Hex())
 fmt.Println("Value (wei):", tx.Value().String())
 fmt.Println("Gas Limit:", tx.Gas())
 fmt.Println("Gas Price (wei):", tx.GasPrice().Uint64())
 fmt.Println("Nonce:", tx.Nonce())
 fmt.Println("Input Data:", hexutil.Encode(tx.Data()))
 if tx.To() != nil {
  fmt.Println("To Address:", tx.To().Hex())
 } else {
  fmt.Println("Contract Creation")
 }
}

However, there's a catch: the transaction object does not directly expose the from address. To derive it, you must recover the sender from the digital signature.

Getting the Sender Address (From Address)

To obtain the from address, you need to reconstruct the transaction message using the chain ID and a signer. Here's how:

chainID, err := client.NetworkID(context.Background())
if err != nil {
 log.Fatal(err)
}

signer := types.NewEIP155Signer(chainID)
for _, tx := range block.Transactions() {
 message, err := tx.AsMessage(signer)
 if err != nil {
  log.Fatal(err)
 }
 from := message.From()
 fmt.Println("From Address:", from.Hex())
}

This step is crucial for applications like wallet tracking, fraud detection, or user behavior analysis—where knowing both sender and receiver is necessary.

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Frequently Asked Questions

Q: Can I scan all Ethereum blocks efficiently?
A: Yes, but scanning every block from genesis onward requires significant resources. It's best to process blocks in batches and store results in a database like PostgreSQL or MongoDB for indexing and querying.

Q: Why can't I get the from address directly from the transaction?
A: The from address isn’t stored in the transaction; it’s derived by verifying the cryptographic signature. That’s why you need a signer and chain ID to recover it.

Q: Do I need my own Ethereum node?
A: Not necessarily. Public APIs like Infura or Alchemy allow you to query blockchain data without running a full node. However, for high-frequency access or privacy, running your own node (e.g., Geth or Erigon) is recommended.

Q: What are common use cases for block scanning?
A: Use cases include building explorers, detecting suspicious transactions, tracking token flows, syncing dApp user balances, and auditing smart contract interactions.

Q: Is it safe to use public endpoints like Infura?
A: Public endpoints are fine for development and light production use. However, they may throttle requests under heavy load. Always secure your API keys and consider rate limiting.

Practical Application: Building a Block Scanner

While this article doesn’t include full database integration code (due to security and redundancy policies), here’s a high-level overview of how to build a persistent scanner:

  1. Start from the latest block or a specified starting point.
  2. Loop through consecutive blocks using BlockByNumber.

  3. For each transaction, extract:

    • Hash
    • From/To addresses
    • Value
    • Timestamp
    • Gas usage
  4. Store structured data in a database with proper indexing on addresses and block numbers.
  5. Handle reorgs by checking parent hashes when backtracking.

Such systems power analytics dashboards, on-chain monitoring tools, and institutional-grade audit platforms.

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Core Keywords

By mastering these techniques, you gain direct access to the raw flow of value and interaction on one of the world’s most important decentralized networks. Whether you're developing infrastructure, conducting research, or securing smart contracts, programmatically reading Ethereum blocks is an indispensable skill.

With efficient design and proper tooling, you can transform terabytes of blockchain logs into actionable insights—powering everything from DeFi dashboards to compliance engines.