viem quickstart

This example shows how to use viem with Sei outside a React context: in a Node.js script, a CLI tool, or a backend service. For React dApps, see wagmi and the frontend guide.

Install

npm install viem

These snippets are TypeScript. To run any of them without a separate build step, use tsx (Node 18+):

npx tsx script.ts

Public client

A public client handles all read-only operations.

import { createPublicClient, http } from 'viem';
import { sei } from 'viem/chains';

const client = createPublicClient({
  chain: sei,
  transport: http(),
});

To use a custom RPC endpoint, pass the URL to http():

const client = createPublicClient({
  chain: sei,
  transport: http('https://evm-rpc.sei-apis.com'),
});

Reading chain data

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

import { formatEther } from 'viem';

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

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

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

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

You are done when you see:

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

The exact numbers are illustrative. Your block number and balance will differ. Note the trailing n: getBlockNumber() and getBalance() return a bigint, while getTransactionCount() returns a number.

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 the same reads that the script above performs, sent directly from your browser.

Edit and run

The buttons above send raw JSON-RPC requests. The sandbox below runs the full viem code from this page: imports, a public client, and several reads. You can edit and re-run it live. You do not need to install anything, connect a wallet, or use a key. The sandbox reads Sei Testnet, so its block number and balances do not match the Sei Mainnet reads above:

Wallet client

A wallet client handles signing and broadcasting transactions.

import { createWalletClient, http } from 'viem';
import { privateKeyToAccount } from 'viem/accounts';
import { sei } from 'viem/chains';

const account = privateKeyToAccount('0xYourPrivateKey');

const walletClient = createWalletClient({
  account,
  chain: sei,
  transport: http(),
});

For browser use, replace http() with custom(window.ethereum). Then call walletClient.getAddresses() to get the connected account.

Sending a transaction

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

import { parseEther } from 'viem';

const hash = await walletClient.sendTransaction({
  to: '0xRecipient',
  value: parseEther('1'),
});

const receipt = await client.waitForTransactionReceipt({ hash });
// receipt is final immediately — Sei has instant finality

Reading a contract

import { parseAbi } from 'viem';

const abi = parseAbi(['function balanceOf(address owner) view returns (uint256)']);

const balance = await client.readContract({
  address: '0xTokenAddress',
  abi,
  functionName: 'balanceOf',
  args: ['0xYourAddress'],
});

Writing to a contract

const hash = await walletClient.writeContract({
  address: '0xTokenAddress',
  abi,
  functionName: 'transfer',
  args: ['0xRecipient', 1_000_000n],
});

const receipt = await client.waitForTransactionReceipt({ hash });

Simulating before writing

const { result } = await client.simulateContract({
  address: '0xTokenAddress',
  abi,
  functionName: 'transfer',
  args: ['0xRecipient', 1_000_000n],
  account,
});

// If simulation succeeds, execute it
const hash = await walletClient.writeContract(result);

Estimating gas

Always use estimateGas instead of hard-coded values. Governance can adjust SSTORE costs on Sei.

const gas = await client.estimateGas({
  account,
  to: '0xContractAddress',
  data: '0xCalldata',
});

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

Overview

Client Setup

Accounts and Transactions

Tokens

Contracts

Sei Features

viem Quickstart

viem quickstart

Install

Public client

Reading chain data

Try it live

Edit and run

Wallet client

Sending a transaction

Reading a contract

Writing to a contract

Simulating before writing

Estimating gas

Next steps

​viem quickstart

​Install

​Public client

​Reading chain data

​Try it live

​Edit and run

​Wallet client

​Sending a transaction

​Reading a contract

​Writing to a contract

​Simulating before writing

​Estimating gas

​Next steps

viem quickstart

Install

Public client

Reading chain data

Try it live

Edit and run

Wallet client

Sending a transaction

Reading a contract

Writing to a contract

Simulating before writing

Estimating gas

Next steps