hoodmane/walrus

Walrus is a toolkit for modifying WebAssembly files. If you've built an app or library that compiles to WebAssembly, a format that runs code in web browsers and other environments, Walrus lets you transform that compiled code after the fact, without rewriting it from scratch. Think of it as a post-processor: you can strip out unused functions, inject new behavior, or restructure the module to optimize it for your needs. Under the hood, Walrus parses a WebAssembly binary and gives you a clean programming interface to inspect and modify its contents. Instead of manually editing raw bytecode (which would be error-prone), you work with higher-level concepts, like functions, imports, and data sections, that the library manages for you. You can add, remove, or rearrange pieces of code and then generate a new, valid WebAssembly file to use in production. This library is built and maintained by the Rust and WebAssembly Working Group, and it already powers the popular wasm-bindgen tool, which helps Rust developers write WebAssembly that talks to JavaScript. If you're creating developer tools in this space, for example, a bundle optimizer, a debugger, or a code minifier for WebAssembly, Walrus removes the complexity of parsing and manipulating the format yourself. It handles the messy details so you can focus on the transformation logic you actually care about. A nice long-term goal mentioned in the README is preserving debug information (DWARF data) through transformations, so developers can step through optimized code as easily as they debug unoptimized versions. The project is still evolving, but it's stable enough that real-world tools already depend on it.