Send CELO & cUSD

Learn how to connect to the Celo test network and transfer tokens using ContractKit
BeginnerNodeJS< 1 hour


In this guide, we are going to write a Node.js script to introduce some of the basic concepts that are important to understand how Celo works. This will get us started with connecting to the Celo network and learning how to develop more advanced applications.

Learning Objectives

At the end of this guide, you will be able to:
  • Connect to the Celo test network, called Alfajores
  • Get test CELO and Celo Dollars (cUSD) from the faucet
  • Read account and contract information from the test network
  • Transferring CELO and cUSD on the test network

Getting Started

To start, clone this GitHub repo. This is a Node.js application.
git clone
We will be using the Celo ContractKit SDK to interact with the Celo test network (Alfajores). Let's install it. It is already defined in the package.json, so we can get it with
npm install

Importing ContractKit

We will be writing our Node.js app in the helloCelo.js file.
Import the contract kit into our script with
// 1. Import web3 and contractkit const Web3 = require("web3") const ContractKit = require('@celo/contractkit')
Now we can use the ContractKit to connect to the test network.
// 2. Init a new kit, connected to the alfajores testnet const web3 = new Web3('') const kit = ContractKit.newKitFromWeb3(web3)

Reading Alfajores

ContractKit contains a contracts property that we can use to access certain information about deployed Celo contracts.
Let's read some token balances from the blockchain. Add the following line in the readAccount() function.
// 3. Get the token contract wrappers let goldtoken = await kit.contracts.getGoldToken() let stabletoken = await kit.contracts.getStableToken()
We can get the CELO balance of an account using the token wrappers like goldtoken.balanceOf(address). Let's check the balance of this address '0xD86518b29BB52a5DAC5991eACf09481CE4B0710d'.
// 4. Address to look up let anAddress = '0xD86518b29BB52a5DAC5991eACf09481CE4B0710d' // 5. Get token balances let celoBalance = await goldtoken.balanceOf(anAddress) let cUSDBalance = await stabletoken.balanceOf(anAddress) // Print balances console.log(`${anAddress} CELO balance: ${celoBalance.toString()}`) console.log(`${anAddress} cUSD balance: ${cUSDBalance.toString()}`)
The balanceOf(address) function also returns a Promise, so we wait for the promise to resolve then we print the result.
To view the balances, run the script from the termainal with
node helloCelo.js
Reading all account balances is a powerful feature of blockchains. Next, let's see how we can send value to each other on the testnet.
In order to do transfers (aka transactions), we need to:
  1. Create an account (by creating a private key)
  2. Fund it with test CELO and cUSDs
  3. Sign and send transactions to the network


We are accessing the Celo network via a remote node via HTTP requests at ''.
Because we are accessing the network remotely, we need to generate an account to sign transactions and fund that account with test CELO.
There is a short script in getAccount.js to either get a Celo account from a mnemonic in the .secret file, or create a random account if the file is empty. In the script, we useweb3.js to create a new private key/account pair. Web3.js is a popular javascript library for handling Ethereum related functionality. Celo is a cousin of Ethereum, so this library works well for generating Celo accounts.
We can now use this account to get account information (ie the private key and account address) and to send transactions from account.address. Add the following code to read the account balance. Continue adding to helloCelo.js.
// Create an Account // 6. Import the getAccount function const getAccount = require('./getAccount').getAccount async function createAccount(){ // 7. Get your account let account = await getAccount() // 8. Get the token contract wrappers let goldtoken = await kit.contracts.getGoldToken() let stabletoken = await kit.contracts.getStableToken() // 9. Get your token balances let celoBalance = await goldtoken.balanceOf(account.address) let cUSDBalance = await stabletoken.balanceOf(account.address) // Print your account info console.log(`Your account address: ${account.address}`) console.log(`Your account CELO balance: ${celoBalance.toString()}`) console.log(`Your account cUSD balance: ${cUSDBalance.toString()}`) }
Run this script again with node helloCelo.js. This will print 0, as we have not funded the associated account yet.

Using the faucet

We can get free test CELO and cUSDs on the test network for development via the Celo Alfajores faucet.
Copy your randomly generated account address from the console output mentioned above, and paste it into the faucet.
Once your account has been funded, run the command node helloCelo.js again to see your updated balance.

Sending Value

We have an account with CELO and cUSD in it, now how do we send tokens to another account? Remember the token wrappers we used to read account balances earlier? We can use the same wrappers to send tokens, you just need to add the private key associated with your account to ContractKit (see line 10).
The token wrappers have a method called transfer(address, amount) that allows you to send value to the specified address (line 14).
You need to send() the transaction to the network after you construct it. The send() methods accepts an option that allows you to specify the feeCurrency, which allows the sender to pay transaction fees in CELO or cUSD. The default feeCurrency is CELO. In the following example, let's pay transaction fees in CELO when we transfer CELO and pay with cUSD when we transfer cUSD.
The send() method returns a transaction object. We will wait for the transaction receipt (which will be returned when the transaction has been included in the blockchain) and print it when we get it. This receipt contains information about the transaction.
After we read the receipt, we check the balance of our account again, using the balanceOf() function. The logs print our updated balance!
You may notice that the account balance is a bit smaller than the amount of tokens that we sent. This is because you have to pay for every update to the network.
Add the following code to the send() function in helloCelo.js to send a transaction.
async function send(){ // 10. Get your account let account = await getAccount() // 11. Add your account to ContractKit to sign transactions kit.connection.addAccount(account.privateKey) // 12. Specify recipient Address let anAddress = '0xD86518b29BB52a5DAC5991eACf09481CE4B0710d' // 13. Specify an amount to send let amount = 100000 // 14. Get the token contract wrappers let goldtoken = await kit.contracts.getGoldToken() let stabletoken = await kit.contracts.getStableToken() // 15. Transfer CELO and cUSD from your account to anAddress // Specify cUSD as the feeCurrency when sending cUSD let celotx = await goldtoken.transfer(anAddress, amount).send({from: account.address}) let cUSDtx = await stabletoken.transfer(anAddress, amount).send({from: account.address, feeCurrency: stabletoken.address}) // 16. Wait for the transactions to be processed let celoReceipt = await celotx.waitReceipt() let cUSDReceipt = await cUSDtx.waitReceipt() // 17. Print receipts console.log('CELO Transaction receipt: %o', celoReceipt) console.log('cUSD Transaction receipt: %o', cUSDReceipt) // 18. Get your new balances let celoBalance = await goldtoken.balanceOf(account.address) let cUSDBalance = await stabletoken.balanceOf(account.address) // 19. Print new balance console.log(`Your new account CELO balance: ${celoBalance.toString()}`) console.log(`Your new account cUSD balance: ${cUSDBalance.toString()}`) }
Run node helloCelo.js again to send the transactions and see the printed output in the console.

Connecting to a Ledger Device from a Web Application

The above instructions apply to building NodeJS applications. If you want to build an integration with a web application, you can still use the ContractKit by following slightly modified instructions.
You will need to have the following npm libraries installed: web3, @celo/contractkit, @celo/wallet-ledger, @ledgerhq/hw-app-eth, @ledgerhq/hw-transport-u2f and @ledgerhq/hw-transport-webusb.
Then, you can create a new instance of the ContractKit with the following code:
import { ContractKit, newKitFromWeb3 } from "@celo/contractkit"; import { newLedgerWalletWithSetup } from "@celo/wallet-ledger"; import Eth from "@ledgerhq/hw-app-eth"; import TransportU2F from "@ledgerhq/hw-transport-u2f"; import TransportUSB from "@ledgerhq/hw-transport-webusb"; import Web3 from "web3"; // Handle getting the Celo Ledger transport. const getCeloLedgerTransport = () => { if (window.USB) { return TransportUSB.create(); } else if (window.u2f) { return TransportU2F.create(); } throw new Error("Ledger Transport not support, please use Chrome, Firefox, Brave, Opera or Edge."); }; // Handle creating a new Celo ContractKit const getContractKit = async () => { // Create a Web3 provider by passing in the testnet/mainnet URL const web3 = new Web3(""); // Get the appropriate Ledger Transport const transport = await getCeloLedgerTransport(); // Create a new instance of the ETH Ledger Wallet library const eth = new Eth(transport); // Use the Celo Ledger Wallet setup util const wallet = await newLedgerWalletWithSetup(eth.transport); // Instantiate the ContractKit const kit: ContractKit = newKitFromWeb3(web3, wallet); return kit; };
Once you have successfully created the ContractKit, you can use the various Celo contracts to sign transactions with a connected Ledger device. For example, here's how to transfer gold tokens (just like above in the NodeJS example):
// Use the gold token contract to transfer tokens const transfer = async (from, to, amount) => { const goldTokenContract = await kit.contracts.getGoldToken(); const tx = await goldTokenContract.transfer(to, amount).send({ from }); const receipt = await tx.waitReceipt(); console.log("Transaction Receipt: ", receipt); };
This is the basic setup to integrate the Celo Ledger App with a web application. You can also view the Celo Ledger App example codebase for some other examples of connecting to a Ledger Device from a web application.


Congratulations! You have accomplished a lot in this short introduction to developing on Celo.
We covered:
  • Installing and setting up ContractKit
  • Connecting to the Celo Alfajores network
  • Getting the CELO contract wrapper
  • Reading account balances using the CELO wrapper
  • Generating a new account in Celo
  • Funding an account using the Celo Alfajores Faucet
  • Sending CELO
If you had any difficulties following this tutorial or simply want to discuss Celo tech with us you can join our community today!
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