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Foundry is a blazing fast, portable and modular toolkit for Ethereum application development written in Rust.

Foundry consists of:

• Forge: Build, test, fuzz, debug and deploy Solidity contracts, like Hardhat, Brownie, Ape.
• Cast: A Swiss Army knife for interacting with EVM smart contracts, sending transactions and getting chain data.
• Anvil: Fast local Ethereum development node, akin to Hardhat Network, Tenderly.
• Chisel: Fast, utilitarian, and verbose Solidity REPL.

Need help getting started with Foundry? Read the 📖 Foundry Book!

Features

• High-Performance Compilation

  • Fast and Flexible: Automatically detects and installs the required Solidity compiler version.
  • Solidity and Vyper Support: Fully supports both Solidity and Vyper out-of-the-box.
  • Incremental Compilation: Re-compiles only changed files, saving time.
  • Parallelized Pipeline: Leverages multi-core systems for ultra-fast builds.
  • Broad Compatibility: Supports non-standard directory structures, including Hardhat repos.

• Advanced Testing

  • No Context Switching: Write tests directly in Solidity.
  • Fuzz Testing: Quickly identify edge cases with input shrinking and counter-example generation.
  • Invariant Testing: Ensure complex system properties hold across a wide range of inputs.
  • Debugging Made Easy: Use forge-std's console.sol for flexible debug logging.
  • Interactive Debugger: Step through your Solidity code with Foundry's interactive debugger, making it easy to pinpoint issues.

• Powerful Runtime Features

  • RPC Forking: Fast and efficient remote RPC forking backed by Alloy.
  • Lightweight & Portable: No dependency on Nix or other package managers for installation.

• Streamlined CI/CD

  • Optimized CI: Accelerate builds, run tests and execute scripts using Foundry's GitHub action.

Installation

Getting started is very easy:

Install foundryup:

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

Next, run foundryup.

It will automatically install the latest version of the precompiled binaries: forge, cast, anvil, and chisel.

foundryup

Done!

For additional details see the installation guide in the Foundry Book.

If you're experiencing any issues while installing, check out Getting Help and the FAQ.

How Fast?

Forge is quite fast at both compiling (leveraging solc with foundry-compilers) and testing.

See the benchmarks below. Older benchmarks against DappTools can be found in the v0.2.0 announcement post and in the Convex Shutdown Simulation repository.

Testing Benchmarks

In the above benchmarks, compilation was always skipped

Takeaway: Forge dramatically outperforms the competition, delivering blazing-fast execution speeds while continuously expanding its robust feature set.

Compilation Benchmarks

 

Takeaway: Forge compilation is consistently faster than Hardhat by a factor of 2.1x to 5.2x, depending on the amount of caching involved.

Forge

Forge helps you build, test, fuzz, debug and deploy Solidity contracts.

The best way to understand Forge is to simply try it (in less than 30 seconds!).

First, let's initialize a new counter example repository:

forge init counter

Next cd into counter and build :

forge build

[⠊] Compiling...
[⠔] Compiling 27 files with Solc 0.8.28
[⠒] Solc 0.8.28 finished in 452.13ms
Compiler run successful!

Let's test our contracts:

forge test

[⠊] Compiling...
No files changed, compilation skipped

Ran 2 tests for test/Counter.t.sol:CounterTest
[PASS] testFuzz_SetNumber(uint256) (runs: 256, μ: 31121, ~: 31277)
[PASS] test_Increment() (gas: 31293)
Suite result: ok. 2 passed; 0 failed; 0 skipped; finished in 5.35ms (4.86ms CPU time)

Ran 1 test suite in 5.91ms (5.35ms CPU time): 2 tests passed, 0 failed, 0 skipped (2 total tests)

Finally, let's run our deployment script:

forge script script/Counter.s.sol

[⠊] Compiling...
No files changed, compilation skipped
Script ran successfully.
Gas used: 109037

If you wish to simulate on-chain transactions pass a RPC URL.

Run forge --help to explore the full list of available subcommands and their usage.

More documentation can be found in the forge section of the Foundry Book.

Cast

Cast is a Swiss Army knife for interacting with Ethereum applications from the command line.

Here are a few examples of what you can do:

Check the latest block on Ethereum Mainnet:

cast block-number --rpc-url https://eth.merkle.io

Check the Ether balance of vitalik.eth

cast balance vitalik.eth --ether --rpc-url https://eth.merkle.io

Replay and trace a transaction

cast run 0x9c32042f5e997e27e67f82583839548eb19dc78c4769ad6218657c17f2a5ed31 --rpc-url https://eth.merkle.io

Optionally, pass --etherscan-api-key <API_KEY> to decode transaction traces using verified source maps, providing more detailed and human-readable information.

Run cast --help to explore the full list of available subcommands and their usage.

More documentation can be found in the cast section of the Foundry Book.

Anvil

Anvil is a fast local Ethereum development node.

Let's fork Ethereum mainnet at the latest block:

anvil --fork-url https://eth.merkle.io

You can use those same cast subcommands against your anvil instance:

cast block-number

Run anvil --help to explore the full list of available features and their usage.

More documentation can be found in the anvil section of the Foundry Book.

Chisel

Chisel is a fast, utilitarian, and verbose Solidity REPL.

To use Chisel, simply type chisel.

chisel

From here, start writing Solidity code! Chisel will offer verbose feedback on each input.

Create a variable a and query it:

➜ uint256 a = 123;
➜ a
Type: uint256
├ Hex: 0x7b
├ Hex (full word): 0x000000000000000000000000000000000000000000000000000000000000007b
└ Decimal: 123

Finally, run !source to see a was applied:

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.28;

import {Vm} from "forge-std/Vm.sol";

contract REPL {
    Vm internal constant vm = Vm(address(uint160(uint256(keccak256("hevm cheat code")))));

    /// @notice REPL contract entry point
    function run() public {
        uint256 a = 123;
    }
}

Run chisel --help to explore the full list of available features and their usage.

More documentation can be found in the chisel section of the Foundry Book.

Configuration

Foundry is highly configurable, allowing you to tailor it to your needs. Configuration is managed via a file called foundry.toml located in the root of your project or any parent directory. For a full list of configuration options, refer to the config package documentation.

Profiles and Namespaces

• Configuration can be organized into profiles, which are arbitrarily namespaced for flexibility.
• The default profile is named default. Learn more in the Default Profile section.
• To select a different profile, set the FOUNDRY_PROFILE environment variable.
• Override specific settings using environment variables prefixed with FOUNDRY_ (e.g., FOUNDRY_SRC).

You can find additional setup and configurations guides in the Foundry Book and in the config crate:

• Configuring with foundry.toml
• Setting up VSCode
• Shell autocompletions

Contributing

See our contributing guidelines.

Getting Help

First, see if the answer to your question can be found in the Foundy Book, or in the relevant crate.

If the answer is not there:

• Join the support Telegram to get help, or
• Open a discussion with your question, or
• Open an issue with the bug

If you want to contribute, or follow along with contributor discussion, you can use our main telegram to chat with us about the development of Foundry!

License

Licensed under either of Apache License, Version 2.0 or MIT License at your option.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in these crates by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

Acknowledgements

• Foundry is a clean-room rewrite of the testing framework DappTools. None of this would have been possible without the DappHub team's work over the years.
• Matthias Seitz: Created ethers-solc (now foundry-compilers) which is the backbone of our compilation pipeline, as well as countless contributions to ethers, in particular the abigen macros.
• Rohit Narurkar: Created the Rust Solidity version manager svm-rs which we use to auto-detect and manage multiple Solidity versions.
• Brock Elmore: For extending the VM's cheatcodes and implementing structured call tracing, a critical feature for debugging smart contract calls.
• All the other contributors to the ethers-rs, alloy & foundry repositories and chatrooms.