WebAssembly (WASM)

A fast, portable coding format making blockchains snappier and cross-platform.

What is WebAssembly (WASM)?

WebAssembly—often shortened to WASM—is like a universal translator for code. It lets developers write code in languages like Rust, C++, or Go and run it at near-native speed anywhere WASM is supported, like web browsers or blockchain environments.

For everyday users, this means smoother experiences and faster applications. For developers, it offers the flexibility to build high-performance programs that work across many systems without rewriting everything from scratch.

WASM compiles high-level code to a lightweight binary format that’s secure, fast, and runs in a controlled environment. In Polkadot, WASM is used not just for smart contracts, but also to power the core logic of entire blockchains, making them safer, more efficient, and easier to upgrade.

How does WASM work?

Developers write code in their preferred language (such as Rust or C++) and compile it to WASM. WASM code runs in a secure virtual machine known as the WASM runtime, which can operate in a web browser or directly onchain.

In Polkadot, both rollups and smart contracts use WASM to execute logic within the platform’s native runtime. This architecture supports forkless upgrades, where the runtime itself can be swapped out for new WASM code through onchain governance, without halting the networking or requiring disruptive chain splits.

Why is WASM important for Polkadot and Web3?

WASM is central to Polkadot’s flexibility and future-proofing. By using WASM as its standard execution format, Polkadot supports forkless upgrades, letting core logic be updated without network disruption. Developers can build in familiar languages like Rust or C++ and target a secure, high-performance runtime shared across the ecosystem.

WASM also enhances Interoperability. As a Web3-wide standard, it powers projects beyond Polkadot, enabling shared tooling and broader compatibility across chains

Benefits of WASM

• Chain upgradability: Upgrade runtime logic without forks.
• Multilingual support: Build blockchain logic in Rust, C++, AssemblyScript, etc.
• Cross-platform: WASM code runs in browsers, servers, and blockchains.
• Smart contracts: Platforms like ink! (for Polkadot) use WASM to execute contracts safely.