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web3.eth.subscribe Migration Guide

Breaking Changes

New Block Headers event

In 1.x, web3.eth.subscribe('newBlockHeaders') was used to subscribe to new block headers.

In 4.x, either web3.eth.subscribe('newHeads') or web3.eth.subscribe('newBlockHeaders') can be used to subscribe to new block headers.


In 1.x, web3.eth.clearSubscriptions returns true on success.

In 4.x, web3.eth.clearSubscriptions returns an Array of subscription ids.

// in 1.x
var subscription = web3.eth.subscribe('newBlockHeaders', function (error, result) {
if (!error) console.log(result);
web3.eth.clearSubscriptions(function (error, success) {
console.log(success); // true

// in 4.x
const subscription = await web3.eth.subscribe('newHeads');
console.log(), // [...] Array of subsription ids