Emits new blocks that are added to the blockchain.

The newHeads subscription type emits an event any time a new header (block) is added to the chain, including during a chain reorganization.


NOTE: Chain Reorganizations (ReOrgs)

When a chain reorganization occurs, this subscription will emit an event containing all new headers (blocks) for the new chain. This means that you may see multiple headers emitted with the same height (block number), and when this happens the later (highest) block number should be taken as the correct one after a reorganization.

Supported Networks



  • None


  • result
    • number: QUANTITY - the block number. null when its pending block.
    • hash: DATA, 32 Bytes - hash of the block. null when its pending block.
    • parentHash: DATA, 32 Bytes - hash of the parent block.
    • nonce: DATA, 8 Bytes - hash of the generated proof-of-work. null when its pending block.
    • sha3Uncles: DATA, 32 Bytes - SHA3 of the uncles data in the block.
    • logsBloom: DATA, 256 Bytes - the bloom filter for the logs of the block. null when its pending block.
    • transactionsRoot: DATA, 32 Bytes - the root of the transaction trie of the block.
    • stateRoot: DATA, 32 Bytes - the root of the final state trie of the block.
    • receiptsRoot: DATA, 32 Bytes - the root of the receipts trie of the block.
    • miner: DATA, 20 Bytes - the address of the beneficiary to whom the mining rewards were given.
    • difficulty: QUANTITY - integer of the difficulty for this block.
    • totalDifficulty: QUANTITY - integer of the total difficulty of the chain until this block.
    • extraData: DATA - the "extra data" field of this block.
    • size: QUANTITY - integer the size of this block in bytes.
    • gasLimit: QUANTITY - the maximum gas allowed in this block.
    • gasUsed: QUANTITY - the total used gas by all transactions in this block.
    • timestamp: QUANTITY - the unix timestamp for when the block was collated.
    • transactions: Array - Array of transaction objects, or 32 Bytes transaction hashes depending on the last given parameter.
    • uncles: Array - Array of uncle hashes.
  • subscription: string - subscription ID


// initiate websocket stream first
wscat -c wss://

// then call subscription 
{"jsonrpc":"2.0","id": 1, "method": "eth_subscribe", "params": ["newHeads"]}
// Installation: npm install alchemy-sdk
import { Alchemy, Network } from "alchemy-sdk";

const settings = {
  apiKey: "demo", // Replace with your Alchemy API Key.
  network: Network.ETH_MAINNET, // Replace with your network.
const alchemy = new Alchemy(settings);

// Subscribe to new blocks, or newHeads"block", (blockNumber) =>
  console.log("Latest block:", blockNumber)


{"jsonrpc":"2.0", "id":1, "result":"0x9ce59a13059e417087c02d3236a0b1cc"}

   "jsonrpc": "2.0",
   "method": "eth_subscription",
   "params": {
     "result": {
       "difficulty": "0x15d9223a23aa",
       "extraData": "0xd983010305844765746887676f312e342e328777696e646f7773",
       "gasLimit": "0x47e7c4",
       "gasUsed": "0x38658",
       "logsBloom": "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
       "miner": "0xf8b483dba2c3b7176a3da549ad41a48bb3121069",
       "nonce": "0x084149998194cc5f",
       "number": "0x1348c9",
       "parentHash": "0x7736fab79e05dc611604d22470dadad26f56fe494421b5b333de816ce1f25701",
       "receiptRoot": "0x2fab35823ad00c7bb388595cb46652fe7886e00660a01e867824d3dceb1c8d36",
       "sha3Uncles": "0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347",
       "stateRoot": "0xb3346685172db67de536d8765c43c31009d0eb3bd9c501c9be3229203f15f378",
       "timestamp": "0x56ffeff8",
       "transactionsRoot": "0x0167ffa60e3ebc0b080cdb95f7c0087dd6c0e61413140e39d94d3468d7c9689f"
   "subscription": "0x9ce59a13059e417087c02d3236a0b1cc"