Identify if a block has been included in the main chain or was forked

const Web3 = require("web3");

const NODE_URL = "YOUR_CHAINSTACK_ENDPOINT"
const web3 = new Web3(NODE_URL)

// If the hash of the block to inspect is === to the parent hash of the next block, then this is not a forked block.
async function isForked(block) {

    const nextBlock = blockToInspect + 1
    console.log(`Block to inspect: ${block}`)
    console.log(`Next block: ${nextBlock} \n`)

    const blockToInspectHash = (await web3.eth.getBlock(block, false)).hash
    console.log(`Block hash of the block you are inspecting: ${blockToInspectHash} \n`)

    const nextBlockParentHash = (await web3.eth.getBlock(nextBlock, false)).parentHash
    console.log(`Parent hash of the next block: ${nextBlockParentHash} \n`)

    if (String(nextBlockParentHash) == String(nextBlockParentHash)) {
        console.log(`You are inspecting the correct block`)
        return false

    } else {
        console.log(`You are inspecting a forked block!`)
        return true
    }
}

const blockToInspect = 16394103
isForked(blockToInspect)

$ node index

  'Block to inspect: 16394103
  'Next block: 16394104

  'Block hash of the block you are inspecting: 0x819f79970003b8c7d51071001509406d9f51aa734aaf69aff506959abdcc2d55

  'Parent hash of the next block: 0x819f79970003b8c7d51071001509406d9f51aa734aaf69aff506959abdcc2d55

  'You are inspecting the correct block

Prerequisites

Environment setup

Initialize a provider instance

Create a new file, index.js, import the web3.js library, and initialize a new provider instance using your Chainstack node URL.

Paste your Chainstack node URL in the NODE_URL const.

index.js

const Web3 = require("web3");

const NODE_URL = "YOUR_CHAINSTACK_ENDPOINT"
const web3 = new Web3(NODE_URL)

Create the function with the logic

Add a function that takes a block number as a parameter, retrieves the block data using the eth_getBlockByNumber method, and compares its hash with the parent hash of the next block.

This function returns true if the block is forked and false if it is not.

You can remove the console.log statements from the function and only use its boolean returns.

index.js

// If the hash of the block to inspect is === to the parent hash of the next block, then this is not a forked block.
async function isForked(block) {

    const nextBlock = blockToInspect + 1
    console.log(`Block to inspect: ${block}`)
    console.log(`Next block: ${nextBlock} \n`)

    const blockToInspectHash = (await web3.eth.getBlock(block, false)).hash
    console.log(`Block hash of the block you are inspecting: ${blockToInspectHash} \n`)

    const nextBlockParentHash = (await web3.eth.getBlock(nextBlock, false)).parentHash
    console.log(`Parent hash of the next block: ${nextBlockParentHash} \n`)

    if (String(nextBlockParentHash) == String(nextBlockParentHash)) {
        console.log(`You are inspecting the correct block`)
        return false

    } else {
        console.log(`You are inspecting a forked block!`)
        return true
    }
}

Call the function

Understand the logic

const Web3 = require("web3");

const NODE_URL = "YOUR_CHAINSTACK_ENDPOINT"
const web3 = new Web3(NODE_URL)

// If the hash of the block to inspect is === to the parent hash of the next block, then this is not a forked block.
async function isForked(block) {

    const nextBlock = blockToInspect + 1
    console.log(`Block to inspect: ${block}`)
    console.log(`Next block: ${nextBlock} \n`)

    const blockToInspectHash = (await web3.eth.getBlock(block, false)).hash
    console.log(`Block hash of the block you are inspecting: ${blockToInspectHash} \n`)

    const nextBlockParentHash = (await web3.eth.getBlock(nextBlock, false)).parentHash
    console.log(`Parent hash of the next block: ${nextBlockParentHash} \n`)

    if (String(nextBlockParentHash) == String(nextBlockParentHash)) {
        console.log(`You are inspecting the correct block`)
        return false

    } else {
        console.log(`You are inspecting a forked block!`)
        return true
    }
}

const blockToInspect = 16394103
isForked(blockToInspect)

$ node index

  'Block to inspect: 16394103
  'Next block: 16394104

  'Block hash of the block you are inspecting: 0x819f79970003b8c7d51071001509406d9f51aa734aaf69aff506959abdcc2d55

  'Parent hash of the next block: 0x819f79970003b8c7d51071001509406d9f51aa734aaf69aff506959abdcc2d55

  'You are inspecting the correct block

Extract 'randao' Value from the Ethereum Beacon Chain Using the Block Details Method How to properly encode topics for eth_getLogs

const Web3 = require("web3");

const NODE_URL = "YOUR_CHAINSTACK_ENDPOINT"
const web3 = new Web3(NODE_URL)

// If the hash of the block to inspect is === to the parent hash of the next block, then this is not a forked block.
async function isForked(block) {

    const nextBlock = blockToInspect + 1
    console.log(`Block to inspect: ${block}`)
    console.log(`Next block: ${nextBlock} \n`)

    const blockToInspectHash = (await web3.eth.getBlock(block, false)).hash
    console.log(`Block hash of the block you are inspecting: ${blockToInspectHash} \n`)

    const nextBlockParentHash = (await web3.eth.getBlock(nextBlock, false)).parentHash
    console.log(`Parent hash of the next block: ${nextBlockParentHash} \n`)

    if (String(nextBlockParentHash) == String(nextBlockParentHash)) {
        console.log(`You are inspecting the correct block`)
        return false

    } else {
        console.log(`You are inspecting a forked block!`)
        return true
    }
}

const blockToInspect = 16394103
isForked(blockToInspect)

$ node index

  'Block to inspect: 16394103
  'Next block: 16394104

  'Block hash of the block you are inspecting: 0x819f79970003b8c7d51071001509406d9f51aa734aaf69aff506959abdcc2d55

  'Parent hash of the next block: 0x819f79970003b8c7d51071001509406d9f51aa734aaf69aff506959abdcc2d55

  'You are inspecting the correct block