viem Quickstart

Using viem with Sei in a Node.js script, CLI tool, or backend service

viem Quickstart

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

Install

npm install viem @sei-js/precompiles

Public Client

A public client handles all read-only operations.

import { createPublicClient, http } from 'viem';
import { sei } from '@sei-js/precompiles/viem';

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 needs no private key.

import { formatEther } from 'viem';

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

const balance = await client.getBalance({ address: '0xYourAddress' }); // bigint, wei
console.log('Balance (SEI):', formatEther(balance));

const nonce = await client.getTransactionCount({ address: '0xYourAddress' }); // number
console.log('Nonce:', nonce);

You’re 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 bigint, while getTransactionCount() returns a number.

Wallet Client

A wallet client handles signing and broadcasting transactions.

import { createWalletClient, http } from 'viem';
import { privateKeyToAccount } from 'viem/accounts';
import { sei } from '@sei-js/precompiles/viem';

const account = privateKeyToAccount('0xYourPrivateKey');

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

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

Sending a Transaction

Next step — this 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 rather than hard-coding values. SSTORE costs on Sei are governance-adjustable.

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

Using Python (web3.py)

Sei is fully EVM-compatible, so any standard Ethereum client works — including Python’s web3.py.

pip install web3

from web3 import Web3

w3 = Web3(Web3.HTTPProvider("https://evm-rpc.sei-apis.com"))

print("Connected:", w3.is_connected())
print("Latest block:", w3.eth.block_number)
print("Chain ID:", w3.eth.chain_id)  # 1329

You’re done when you see:

Connected: True
Latest block: 148203117
Chain ID: 1329

The block number is illustrative; the chain ID is always 1329 on mainnet.

Next Steps

• ERC-20 interaction — full token read/write examples
• ERC-721 interaction — NFT ownership, transfers, and approvals
• Pointer contracts — interact with CosmWasm tokens via ERC interfaces
• WebSocket connections — real-time block and event subscriptions