Use web3.js without MetaMask

Question

I have How to use this web3.js on browsers without MetaMask (for read-only Ethereum queries): const web3 = new Web3(window.web3.currentProvider); fails because window.web3 is undefined. I think, I can initialize Web3 by specifying a provider manually. But how to decide what exactly to pass as the argument to new Web3 (for mainnet and for rinkeby)? I need to use my own Infura account? Maybe I can pass the MetaMask's account (is it legal? what is the MetaMask provider URLs for mainnet and for rinkeby)?

owl · Answer

Also you can use infura
Check this page
And use this code:
web3 = new Web3(new Web3.providers.HttpProvider("https://ropsten.infura.io/v3/3c6/*your own Id from infura site after creating project*/753"));

MentatX · Answer

Notice that new API is available:

// Legacy dapp browsers...
if (window.web3 !== undefined) {
    const provider = new Web3.providers.HttpProvider(window.web3.currentProvider);
    const web3 = new Web3(provider);
}

// Modern dapp browsers...
if (window.ethereum !== undefined) {
  const provider = new Web3.providers.HttpProvider(window.ethereum);
  const web3 = new Web3(provider);
}

More details:

https://medium.com/metamask/no-longer-injecting-web3-js-4a899ad6e59e
https://medium.com/metamask/breaking-changes-to-the-metamask-inpage-provider-b4dde069dd0a
https://docs.metamask.io/guide/getting-started.html

In the browser, it is better not to use own account, but only a public Infura API.
Yes, you can pass the MetaMask's account.
Listen to chainChanged event to handle chain change: https://docs.metamask.io/guide/ethereum-provider.html#using-the-provider

Use web3.js without MetaMask

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