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What is foundry?

foundry-rs/foundry — explained in plain English

Analysis updated 2026-06-24

10,343RustAudience · developerComplexity · 4/5LicenseSetup · moderate

In one sentence

A fast Rust-based toolkit for Ethereum smart contract developers, write, test, fuzz, and deploy Solidity contracts from the command line.

Mindmap

mindmap
  root((foundry))
    Tools
      Forge build and test
      Cast blockchain CLI
      Anvil local node
      Chisel Solidity REPL
    Testing
      Unit tests
      Fuzz testing
      Deployment scripts
    Target chain
      Ethereum
      EVM compatible
    Audience
      Smart contract devs
      Blockchain engineers
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filefunction / class

What do people build with it?

USE CASE 1

Write and run automated tests for Solidity smart contracts, including fuzz tests that auto-generate edge-case inputs.

USE CASE 2

Spin up a local Ethereum node with Anvil to develop and test contracts without spending real cryptocurrency.

USE CASE 3

Deploy a Solidity contract to a testnet or mainnet using Forge from a single terminal command.

USE CASE 4

Interactively explore and debug Solidity code expressions one line at a time using the Chisel REPL.

What is it built with?

RustSolidity

How does it compare?

foundry-rs/foundryseanmonstar/warprust-bakery/nom
Stars10,34310,31710,390
LanguageRustRustRust
Setup difficultymoderatemoderateeasy
Complexity4/53/53/5
Audiencedeveloperdeveloperdeveloper

Figures from each repo's GitHub metadata at analysis time.

How do you get it running?

Difficulty · moderate Time to first run · 30min

Requires familiarity with Solidity and Ethereum concepts, installation is two terminal commands but the learning curve for smart contract development is steep.

Use freely for any purpose, including commercial projects, under your choice of the Apache 2.0 or MIT license.

So what is it?

Foundry is a development toolkit for building and testing smart contracts on Ethereum. Ethereum is a blockchain platform where programs called smart contracts run on a decentralized network. Writing and deploying those contracts requires specialized tooling, and Foundry provides a full suite of command-line tools for that work. The toolkit ships four main components. Forge handles building, testing, fuzzing, and deploying Solidity contracts. Solidity is the most common programming language for writing Ethereum smart contracts. Forge's testing capabilities include fuzz testing, which automatically generates many different inputs to find edge cases and bugs. Cast is a general-purpose command-line tool for reading data from the blockchain and sending transactions, described in the README as a Swiss Army knife for interacting with the Ethereum network. Anvil is a local Ethereum node you run on your own machine for development and testing, so you can experiment without using real money or connecting to the live network. Chisel is an interactive Solidity environment, letting developers type and evaluate code expressions one at a time. The project is written in Rust and emphasizes speed. Installation takes two commands from a terminal: a download script, then a second command that fetches the tools. No package manager setup or build process is required for users who just want to use the tools. Foundry is aimed at developers who write Ethereum smart contracts professionally or as a hobby. It assumes familiarity with Solidity and blockchain concepts. Full documentation is available on the project website. The code is open source under a dual Apache 2.0 and MIT license, and community discussion happens on a public Telegram channel.

Copy-paste prompts

Prompt 1
I'm writing my first Solidity ERC-20 token contract. Show me how to set up a Foundry project, write a basic Forge test for the transfer function, and run fuzz testing against it.
Prompt 2
Walk me through using Anvil to start a local Ethereum node, deploy a contract to it with Forge, and then call a read function on that contract using Cast.
Prompt 3
I have a deployed contract on Sepolia testnet. Write the Cast command to read a specific storage slot value and call a view function on it.
Prompt 4
How do I set up Chisel in Foundry to interactively test a Solidity function expression without writing a full contract file?

Frequently asked questions

What is foundry?

A fast Rust-based toolkit for Ethereum smart contract developers, write, test, fuzz, and deploy Solidity contracts from the command line.

What language is foundry written in?

Mainly Rust. The stack also includes Rust, Solidity.

What license does foundry use?

Use freely for any purpose, including commercial projects, under your choice of the Apache 2.0 or MIT license.

How hard is foundry to set up?

Setup difficulty is rated moderate, with roughly 30min to a first successful run.

Who is foundry for?

Mainly developer.

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