Foundry (Ethereum Toolkit)

Foundry is a blazing fast, portable, and modular toolkit for Ethereum application development written in Rust, developed by Georgios Konstantopoulos and the team at Paradigm (a cryptocurrency investment firm). Released as open-source in 2021, Foundry has become one of the two leading smart contract development frameworks alongside Hardhat, with over 8,000 stars as of 2026. Unlike Hardhat which is JavaScript-based, Foundry is compiled to native code, making it significantly faster for compilation, testing, and deployment. The toolkit consists of four main tools: Forge (the Ethereum testing framework supporting Solidity-based tests, fuzz testing with automatic input generation, invariant testing for stateful property verification, coverage analysis, and test traces with call debugging), Cast (a command-line tool for interacting with Ethereum nodes, performing RPC calls, decoding transaction data, sending transactions, and querying on-chain state), Anvil (a local testnet node that mimbers Ethereum mainnet behavior, supporting forking mainnet state, mining modes including automine and interval mining, and JSON-RPC API compatible with all standard Ethereum tools), and Chisel (a Solidity REPL for quick smart contract prototyping and testing). Key features include: fast compilation using solc compiler caching and parallel builds, remappings for import path resolution, script-based deployment with Solidity (writing deployment logic directly in Solidity scripts that can simulate and broadcast transactions across multiple chains), fuzz test configuration with configurable runs and maximum reject counts, invariant test support with configurable depth and fail-on-revert options, test traces with detailed call stacks and gas reporting, fork testing (running tests against mainnet state via Anvil), integration with fuzzing dictionaries, and broadcast transaction management.