ethers v6 Quickstart

Using ethers v6 with Sei in a Node.js script or browser context

ethers v6 quickstart

This example shows how to use ethers v6 with Sei. The patterns apply whether you write a Node.js script, a CLI tool, or a browser dApp.

Install

npm install ethers

These snippets are TypeScript, and they use top-level await. To run one without a separate build step, save it as script.mts and use tsx (Node 18+):

npx tsx script.mts

The .mts extension tells Node.js to treat the file as an ES module. If you use a plain .ts file in a new npm project, tsx fails with Top-level await is currently not supported with the "cjs" output format.

Read-only provider

import { ethers } from 'ethers';

const provider = new ethers.JsonRpcProvider('https://evm-rpc.sei-apis.com');

Reading chain data

This is the first milestone. It does not need a private key.

// Any valid Sei EVM address — swap in your own
const address = '0x0000000000000000000000000000000000000000';

const blockNumber = await provider.getBlockNumber(); // number
console.log('Block number:', blockNumber);

const balance = await provider.getBalance(address); // bigint, wei
console.log('Balance (SEI):', ethers.formatEther(balance));

const nonce = await provider.getTransactionCount(address); // number
console.log('Nonce:', nonce);

You are done when you see:

Block number: 148203117
Balance (SEI): 12.5
Nonce: 7

The exact numbers are illustrative. Your block number and balance will differ. getBlockNumber() and getTransactionCount() return a number, while getBalance() returns a bigint in wei. To format the balance, use ethers.formatEther().

Try it live

Run these read-only calls against Sei Mainnet. You do not need to install anything or use a private key. They are plain JSON-RPC calls, the same reads that the script above performs.

Edit and run

Edit and re-run the full ethers code from this page live in the browser. The sandbox uses a real ethers v6 JsonRpcProvider that reads Sei Testnet. Its block number and balances therefore do not match the Sei Mainnet reads above:

Browser provider

In a browser context, connect to the user’s injected wallet:

const provider = new ethers.BrowserProvider(window.ethereum);
const signer = await provider.getSigner();
const address = await signer.getAddress();

Wallet from private key

Use this pattern in scripts and backend services:

const wallet = new ethers.Wallet('0xYourPrivateKey', provider);

Sending a transaction

This next step requires a funded account. Get testnet SEI from the faucet.

const tx = await wallet.sendTransaction({
  to: '0xRecipient',
  value: ethers.parseEther('1'),
});

const receipt = await tx.wait();
// receipt is final immediately — Sei has instant finality

Reading a contract

const abi = ['function balanceOf(address owner) view returns (uint256)'];
const contract = new ethers.Contract('0xTokenAddress', abi, provider);

const balance = await contract.balanceOf('0xYourAddress');

Writing to a contract

For write operations, pass a signer (a wallet or a browser signer) to the contract constructor:

const contract = new ethers.Contract('0xTokenAddress', abi, wallet);

const tx = await contract.transfer('0xRecipient', 1_000_000n);
const receipt = await tx.wait();

Estimating gas

const gas = await provider.estimateGas({
  from: wallet.address,
  to: '0xContractAddress',
  data: '0xCalldata',
});

Listening for events

Listen for new events over the WebSocket endpoint. Listeners that poll the public HTTP endpoint can miss events or report them twice. The contract needs the event in its ABI:

const wsProvider = new ethers.WebSocketProvider('wss://evm-ws.sei-apis.com');
const token = new ethers.Contract(
  '0xTokenAddress',
  ['event Transfer(address indexed from, address indexed to, uint256 value)'],
  wsProvider
);

token.on('Transfer', (from, to, value) => {
  console.log('Transfer:', { from, to, value });
});

// To stop: await token.off('Transfer'); await wsProvider.destroy();

For past events and more examples, see Listen to events.

Next steps

• Python quickstart (web3.py): the same first steps in Python
• ERC-20 interaction: full token read and write examples
• ERC-721 interaction: NFT ownership, transfers, and approvals
• Pointer contracts: interact with CosmWasm tokens through ERC interfaces
• WebSocket connections: real-time block and event subscriptions