dev-tooling/hardhat-vs-foundry

Hardhat vs Foundry Selection Guide

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v1.0.0·Updated 3/20/2026

Core Differences at a Glance

Dimension	Hardhat	Foundry
Language	JavaScript/TypeScript	Rust + Solidity tests
Testing Approach	Write tests in JS (ethers/viem)	Write tests in Solidity (forge-std)
Speed	Slower (JS runtime)	Extremely fast (Rust compiled, concurrent execution)
Fuzz Testing	Requires plugins	Built-in, enable in one line
Debugging	console.log, can fork mainnet	forge debug, trace level
Plugin Ecosystem	Mature (hardhat-deploy/upgrades)	Growing
Learning Curve	Low (just need JS)	Medium (need to understand Solidity testing)
Deployment Scripts	JS/TS scripts	Solidity Script (forge script)
Community	Larger, more comprehensive docs	Rapidly growing, Paradigm-led

Scenarios for Choosing Foundry

# Quick installation
curl -L https://foundry.paradigm.xyz | bash && foundryup

# Create new project
forge init my-project && cd my-project

# Testing (10-100x faster than Hardhat)
forge test
forge test -vvv
forge test --match-test testFuzz

# Fuzz testing: functions accepting parameters automatically fuzz
# function testFuzz_transfer(uint256 amount) public { ... }

# Fork mainnet testing
forge test --fork-url https://eth-mainnet.alchemyapi.io/v2/KEY

# Gas reports
forge test --gas-report

Choose Foundry if:

Pure contract project with no complex frontend integration
Need extensive fuzz/invariant testing
Care about CI time (test speed)
Team is proficient in Solidity

Scenarios for Choosing Hardhat

npm install --save-dev hardhat && npx hardhat init

# hardhat-deploy (recommended)
npm install --save-dev hardhat-deploy

# OZ Upgrades plugin
npm install @openzeppelin/hardhat-upgrades

Choose Hardhat if:

Full-stack project, frontend needs artifacts/typechain
Using hardhat-deploy for complex deployment workflows
Need OpenZeppelin Upgrades plugin
Team has JS/TS background

Hybrid Approach (Best Practice for Mature Projects)

Many protocols use both: Foundry for unit/fuzz tests (speed), Hardhat for deployment scripts (rich ecosystem).

my-project/
├── foundry.toml       # Foundry config
├── hardhat.config.ts  # Hardhat config
├── src/               # Contracts (shared)
├── test/              # Foundry tests (.t.sol)
└── scripts/           # Hardhat deployment scripts (.ts)

Quick Command Reference

# Foundry
forge build && forge test
forge script Deploy.s.sol --rpc-url $RPC --broadcast
cast call $ADDR "balanceOf(address)(uint256)" $USER
cast send $ADDR "transfer(address,uint256)" $TO $AMT --private-key $KEY

# Hardhat
npx hardhat compile && npx hardhat test
npx hardhat run scripts/deploy.ts --network mainnet
npx hardhat verify --network mainnet $ADDR