This introduction is for developers who want to build on Arbitrum using popular programming languages, like Rust. This capability is made possible by Stylus, a new way to write EVM-compatible smart contracts using your favorite programming languages.
Stylus is an upgrade to Arbitrum Nitro, the tech stack powering Arbitrum One, Arbitrum Nova, and Arbitrum Orbit chains. This upgrade adds a second, coequal virtual machine to the EVM, where EVM contracts continue to behave exactly as they would in Ethereum. We call this paradigm EVM+ since everything is entirely additive.
This second virtual machine executes WebAssembly (WASM) rather than EVM bytecode. WASM is a modern binary format popularized by its use in major web standards, browsers, and companies to speed up computation. Built to be fast, portable, and human-readable, WASM also has sandboxed execution environments for security and simplicity. Working with WASM is nothing new for Arbitrum chains. Ever since the Nitro upgrade, WASM has been a fundamental component of Arbitrum's fully functioning fraud proofs.
With a WASM VM, any programming language that can compile down to WASM are within the bounds of Stylus. While many popular programming languages can be compiled into WASM, some compilers are more suitable for smart contract development than others, like with Rust, C, and C++. Other languages, such as Go, Sway, Move, and Cairo, can be supported as well. Languages that include their own runtimes, like Python and Javascript, are harder for Stylus to support, although not impossible. Third-party contribution in the form of libraries for new and existing languages is welcomed!
Compared to using Solidity, WASM programs are much more efficient. There are many reasons for this, including the decades of compiler development for Rust and C. WASM also has a faster runtime than the EVM, resulting in faster execution. Generally, a 10x improvement has been seen for contracts using WASM languages compared to contracts using Solidity.