The SEI SDK provides developers with a unified toolkit for building high-performance smart contracts and blockchain applications on SEI, offering EVM compatibility, Cosmos SDK modules, fast APIs, and seamless integration with modern development frameworks like Hardhat, Foundry, and ethers.js.
SEI’s developer stack is designed to make building real-time dApps—such as trading platforms, DeFi protocols, games, and payment applications—as fast and intuitive as building on Ethereum, but with the speed and parallel execution benefits of SEI’s architecture.

This guide breaks down the SEI SDK, its key components, and the complete development workflow for building on SEI.

What Is the SEI SDK?

The SEI SDK is the complete suite of tools, frameworks, libraries, APIs, and workflows that developers use to build, test, deploy, and scale applications on the SEI blockchain.

It includes:

The SEI Virtual Machine (EVM-compatible)
Cosmos SDK tooling
Smart contract libraries
RPC endpoints & APIs
Wallet integrations
Node infrastructure
Testing and deployment frameworks

The SEI SDK merges the flexibility of Ethereum development with the performance and interoperability of Cosmos.

Core Components of the SEI SDK

1. SEI VM (SEI Virtual Machine)

SEI’s smart contract runtime.

Features

Fully EVM-compatible
Optimized for parallel execution
Fast bytecode processing
MEV-minimized environment
Supports Solidity and Ethereum tooling

SEI VM allows developers to port Ethereum dApps with zero code changes.

2. Cosmos SDK Integration

SEI is built on the Cosmos SDK, which brings:

Modular chain functionality
Governance modules
Staking & slashing logic
IBC (Inter-Blockchain Communication)
Cross-chain messaging

Developers can build hybrid dApps that use:

EVM for smart contracts
Cosmos modules for chain-level logic

This is unique to SEI.

3. RPC & API Endpoints

SEI exposes standard RPC endpoints found in EVM networks:

eth_call
eth_sendRawTransaction
eth_getBalance
eth_blockNumber
WebSocket live updates
Log + event subscriptions

These are compatible with:

MetaMask
ethers.js
web3.js
Hardhat
Foundry

4. SEI Developer Tools & Frameworks

The SEI SDK supports the complete Ethereum developer ecosystem.

Smart Contract Tooling

Hardhat – compilation, testing, deployment
Foundry – fast, Rust-based smart contract testing
Truffle – legacy support
Brownie – Python-based smart contract development

Libraries

ethers.js
web3.js

Wallets

MetaMask
WalletConnect
Rabby
Leap Wallet (Cosmos-native)

Smart Contract Standards

ERC-20
ERC-721
ERC-1155
Custom SEI extensions

5. Block Explorers

SEI provides Ethereum-style explorers for:

contract verification
transaction tracing
logs & events
wallet activity

These tools support developer debugging and dApp monitoring.

Development Workflow Using the SEI SDK

Below is the typical workflow for building a smart contract or dApp on SEI.

Step 1 — Set Up SEI Development Environment

Install Hardhat


npm install --save-dev hardhat

Initialize project


npx hardhat init

Add SEI network config


module.exports = {
  networks: {
    sei: {
      url: "https://sei-evm-rpc.com", // replace with official RPC
      accounts: [PRIVATE_KEY]
    }
  },
  solidity: "0.8.20",
};

SEI testnet and mainnet can be added with standard RPC URLs.

Step 2 — Write Solidity Smart Contracts

Example contract:


// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

contract SEIDemo {
    uint256 public value;

    function setValue(uint256 newValue) public {
        value = newValue;
    }
}

Because SEI is fully EVM-compatible, all Ethereum smart contract code works natively.

Step 3 — Compile Contracts


npx hardhat compile

Step 4 — Deploy to SEI


npx hardhat run scripts/deploy.js --network sei

Deployment takes less than a second thanks to SEI’s sub-second finality.

Step 5 — Interact With Contracts (Ethers.js)


const { ethers } = require("ethers");

const provider = new ethers.JsonRpcProvider("https://sei-evm-rpc.com");
const contract = new ethers.Contract(address, ABI, provider);

await contract.setValue(42);

The same code works on Ethereum, Arbitrum, Polygon, and SEI.

Step 6 — Frontend Integration

Frontend developers can use:

Next.js
React
Wagmi
RainbowKit
ethers.js
Web3Modal

All standard Ethereum dApp tooling works on SEI out of the box.

Step 7 — Testing & Local Development

Local environments

Hardhat Network
Anvil (Foundry)
SEI testnet

Testing tools

Hardhat test runner
Foundry FFI testing
Chai + Mocha
Solhint + Slither (security)

Step 8 — Monitor & Scale

SEI provides tooling for:

contract verification
event indexing
transaction logs
performance analytics

Node providers such as:

Alchemy
QuickNode
Lava
HashKey

may support SEI endpoints as the ecosystem grows.

Why Developers Choose SEI

1. EVM compatibility + Cosmos interoperability

Hybrid development is becoming a powerful trend:

EVM for smart contracts
IBC for cross-chain operations

Developers build apps that span multiple ecosystems effortlessly.

2. Trading-Optimized Architecture

SEI outperforms other L1s due to:

parallel execution
sub-second finality
MEV minimization
deterministic order sequencing

This is ideal for:

DEXs
derivative platforms
HFT strategies
automated trading bots

3. Real-Time Application Support

SEI’s speed enables:

multiplayer on-chain games
in-game asset updates
NFT auctions
instant payments

4. Lower Fees + Higher Throughput

Developers get:

predictable costs
reliability under load
scaled performance at no extra complexity

Use Cases Enabled by the SEI SDK

DeFi

Orderbooks
Perpetuals
Lending platforms
Options
Automated market makers

Gaming

Real-time worlds
Dynamic NFTs
On-chain action loops

Payments

Microtransactions
Remittance apps
Instant settlement

Infrastructure

Bridges
Indexers
Cross-chain liquidity routes

Conclusion

The SEI SDK gives developers everything they need to build high-performance, EVM-compatible, real-time decentralized applications.
With SEI’s VM, parallel execution engine, sub-second finality, Cosmos SDK modules, and support for all major Ethereum tooling, developers can build sophisticated apps with ease—and deploy them on one of the fastest Layer-1s in the industry.

Whether you’re building trading platforms, DeFi protocols, games, or real-time user experiences, SEI provides the tools and performance needed to build next-generation Web3 applications.

SEI SDK Explained: Tools, Frameworks & Development Workflow