I want to connect to the Ropsten test-net:

    // Is there is an injected web3 instance?
    if (typeof web3 !== 'undefined') {
      App.web3Provider = web3.currentProvider;
      web3 = new Web3(web3.currentProvider);
    } else {
      // If no injected web3 instance is detected, fallback to the TestRPC.
      App.web3Provider = new web3.providers.HttpProvider('http://localhost:8545');
      web3 = new Web3(App.web3Provider);

I have http://localhost:8545 in this code. How do I connect to Ropsten instead of http://localhost:8545?


3 Answers 3


You can either run a local node and specify your chain using --chain ropsten when starting geth/parity and connect to localhost once sync is completed or you can connect to infura.io:

var web3 = new Web3(new Web3.providers.HttpProvider(
  • geth --testnet --chain ropsten --rpc Got this error: Incorrect Usage. flag provided but not defined: -chain Apr 18, 2018 at 17:01
  • 1
    @MuhammadShahzad try omitting --testnet
    – d9ngle
    Apr 18, 2018 at 19:00
  • web3.eth.personal.currentProvider.connected = false for me. Tried Infura ropsten, kovan and local ganache. Sep 7, 2020 at 0:18

You can also install metamask, which will inject web3 into the javascript runtime environment (assuming you are running this in the browser). From metamask, you can then select the chain/network as shown:

Metamask dropdown

  • For using this approach wee should run webpage on local server. May 30, 2019 at 8:49

To get infura links, please use : https://infura.io/

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