Setup Solidity Contracts

Set up a Solidity smart contract project with OpenZeppelin Contracts. Use when users need to: (1) create a new Hardhat or Foundry project, (2) install OpenZeppelin Contracts dependencies for Solidity, (3) configure remappings for Foundry, or (4) understand Solidity import conventions for OpenZeppelin.

Solidity Setup

For existing projects, detect the framework by looking for hardhat.config.* (Hardhat) or foundry.toml (Foundry). For new projects, ask the user which framework they prefer.

Hardhat Setup

• Initialize project (only if starting a new project)

npx hardhat init        # Hardhat v2
npx hardhat --init      # Hardhat v3

• Install OpenZeppelin Contracts:

npm install @openzeppelin/contracts

• If using upgradeable contracts, also install the upgradeable variant:

npm install @openzeppelin/contracts-upgradeable

Foundry Setup

• Install Foundry

curl -L https://foundry.paradigm.xyz | bash
foundryup

• Initialize project (only if starting a new project)

forge init my-project
cd my-project

• Add OpenZeppelin Contracts:

forge install OpenZeppelin/openzeppelin-contracts@v<VERSION>

• If using upgradeable contracts, also add the upgradeable variant:

forge install OpenZeppelin/openzeppelin-contracts-upgradeable@v<VERSION>

Look up the current version from https://github.com/OpenZeppelin/openzeppelin-contracts/releases. Pin to a release tag — without one, forge install pulls the default branch, which may be unstable.

• remappings.txt (if not using upgradeable contracts)

@openzeppelin/contracts/=lib/openzeppelin-contracts/contracts/

• remappings.txt (if using upgradeable contracts)

@openzeppelin/contracts/=lib/openzeppelin-contracts-upgradeable/lib/openzeppelin-contracts/contracts/
@openzeppelin/contracts-upgradeable/=lib/openzeppelin-contracts-upgradeable/contracts/

Note The above remappings mean that both @openzeppelin/contracts/ (including proxy contracts) and @openzeppelin/contracts-upgradeable/ come from the openzeppelin-contracts-upgradeable submodule and its subdirectories, which includes its own transitive copy of openzeppelin-contracts of the same release version number. This format is needed for Etherscan verification to work. Particularly, any copies of openzeppelin-contracts that are installed separately are NOT used.

Compiler version: OpenZeppelin Contracts v5 requires pragma solidity ^0.8.20. If deploying to chains that do not support the PUSH0 opcode (some L2s), set the EVM version to paris in the compiler configuration (e.g., evmVersion: "paris" in Hardhat, evm_version = "paris" in foundry.toml).

Import Conventions

• Standard: @openzeppelin/contracts/token/ERC20/ERC20.sol
• Upgradeable: @openzeppelin/contracts-upgradeable/token/ERC20/ERC20Upgradeable.sol
• Use upgradeable variants only when deploying behind proxies; otherwise use standard contracts.