viem

Viem

Overview

Viem is a TypeScript interface for Ethereum that provides low-level stateless primitives for interacting with the blockchain. It focuses on developer experience, stability, bundle size, and performance.

Key features:

• Automatic type safety and inference
• Tree-shakable lightweight modules
• Optimized encoding/parsing
• Composable APIs

Core Concepts

Concept	Description
Clients	PublicClient, WalletClient, TestClient - entry points
Transports	Connection layer (http, webSocket, custom)
Actions	Operations like getBlockNumber, sendTransaction
Chains	Chain configurations (mainnet, sepolia, arbitrum, etc.)

Constants

Viem exports useful constants for common values:

import { maxUint256, maxUint128, maxInt256, zeroAddress, zeroHash } from "viem";

// Max values for uint types
maxUint256; // 2n ** 256n - 1n
maxUint128; // 2n ** 128n - 1n

// Zero values
zeroAddress; // 0x0000000000000000000000000000000000000000
zeroHash; // 0x0000000000000000000000000000000000000000000000000000000000000000

Utilities

Unit Conversion

Convert between wei and human-readable values:

import { parseEther, formatEther, parseUnits, formatUnits } from "viem";

// ETH <-> Wei (18 decimals)
parseEther("1"); // 1000000000000000000n
formatEther(1000000000000000000n); // "1"

// Custom decimals (e.g., USDC with 6 decimals)
parseUnits("100", 6); // 100000000n
formatUnits(100000000n, 6); // "100"

ABI Utilities

Parse human-readable ABIs:

import { parseAbi, parseAbiItem } from "viem";

const abi = parseAbi([
  "function balanceOf(address owner) view returns (uint256)",
  "function transfer(address to, uint256 amount) returns (bool)",
  "event Transfer(address indexed from, address indexed to, uint256 amount)",
]);

const item = parseAbiItem("function name() view returns (string)");