Showing content from https://rustwasm.github.io/docs/wasm-bindgen/reference/optimize-size.html below:
Optimizing for Size - The `wasm-bindgen` Guide
- Introduction
- 1. Examples
-
- 1.1. Hello, World!
- 1.2. Using console.log
- 1.3. Small Wasm files
- 1.4. Without a Bundler
- 1.5. Synchronous Instantiation
- 1.6. Importing functions from JS
- 1.7. Working with char
- 1.8. js-sys: WebAssembly in WebAssembly
- 1.9. web-sys: DOM hello world
- 1.10. web-sys: Closures
- 1.11. web-sys: performance.now
- 1.12. web-sys: using fetch
- 1.13. web-sys: Weather report
- 1.14. web-sys: canvas hello world
- 1.15. web-sys: canvas Julia set
- 1.16. web-sys: WebAudio
- 1.17. web-sys: WebGL
- 1.18. web-sys: WebSockets
- 1.19. web-sys: WebRTC DataChannel
- 1.20. web-sys: requestAnimationFrame
- 1.21. web-sys: A Simple Paint Program
- 1.22. web-sys: Wasm in Web Worker
- 1.23. Parallel Raytracing
- 1.24. Wasm Audio Worklet
- 1.25. web-sys: A TODO MVC App
- 2. Reference
-
- 2.1. Deployment
- 2.2. JS snippets
- 2.3. Static JS Objects
- 2.4. Passing Rust Closures to JS
- 2.5. Receiving JS Closures in Rust
- 2.6. Promises and Futures
- 2.7. Iterating over JS Values
- 2.8. Arbitrary Data with Serde
- 2.9. Accessing Properties of Untyped JS Values
- 2.10. Working with Duck-Typed Interfaces
- 2.11. Command Line Interface
- 2.12. Optimizing for Size
- 2.13. Supported Rust Targets
- 2.14. Supported Browsers
- 2.15. Support for Weak References
- 2.16. Support for Reference Types
- 2.17. Supported Types
-
- 2.17.1. Imported JavaScript Types
- 2.17.2. Exported Rust Types
- 2.17.3. JsValue
- 2.17.4. Box<[T]> and Vec
- 2.17.5. *const T and *mut T
- 2.17.6. NonNull
- 2.17.7. Numbers
- 2.17.8. bool
- 2.17.9. char
- 2.17.10. str
- 2.17.11. String
- 2.17.12. Number Slices
- 2.17.13. Boxed Number Slices
- 2.17.14. Result<T, E>
- 2.18. #[wasm_bindgen] Attributes
-
- 2.18.1. On JavaScript Imports
-
- 2.18.1.1. catch
- 2.18.1.2. constructor
- 2.18.1.3. extends
- 2.18.1.4. getter and setter
- 2.18.1.5. final
- 2.18.1.6. indexing_getter, indexing_setter, and indexing_deleter
- 2.18.1.7. js_class = "Blah"
- 2.18.1.8. js_name
- 2.18.1.9. js_namespace
- 2.18.1.10. method
- 2.18.1.11. module = "blah"
- 2.18.1.12. raw_module = "blah"
- 2.18.1.13. no_deref
- 2.18.1.14. static_method_of = Blah
- 2.18.1.15. structural
- 2.18.1.16. typescript_type
- 2.18.1.17. variadic
- 2.18.1.18. vendor_prefix
- 2.18.2. On Rust Exports
-
- 2.18.2.1. constructor
- 2.18.2.2. js_name = Blah
- 2.18.2.3. js_class = Blah
- 2.18.2.4. readonly
- 2.18.2.5. skip
- 2.18.2.6. skip_jsdoc
- 2.18.2.7. start
- 2.18.2.8. main
- 2.18.2.9. typescript_custom_section
- 2.18.2.10. getter and setter
- 2.18.2.11. inspectable
- 2.18.2.12. skip_typescript
- 2.18.2.13. getter_with_clone
- 2.18.2.14. unchecked_return_type and unchecked_param_type
- 2.18.2.15. return_description and param_description
- 3. web-sys
-
- 3.1. Using web-sys
- 3.2. Cargo Features
- 3.3. Function Overloads
- 3.4. Type Translations
- 3.5. Inheritance
- 3.6. Unstable APIs
- 4. Testing with wasm-bindgen-test
-
- 4.1. Usage
- 4.2. Writing Asynchronous Tests
- 4.3. Testing in Headless Browsers
- 4.4. Continuous Integration
- 4.5. Coverage (Experimental)
- 5. Contributing to wasm-bindgen
-
- 5.1. Testing
- 5.2. Internal Design
-
- 5.2.1. JS Objects in Rust
- 5.2.2. Exporting a function to JS
- 5.2.3. Exporting a struct to JS
- 5.2.4. Importing a function from JS
- 5.2.5. Importing a class from JS
- 5.2.6. Rust Type conversions
- 5.2.7. Types in wasm-bindgen
- 5.3. js-sys
-
- 5.3.1. Testing
- 5.3.2. Adding More APIs
- 5.4. web-sys
-
- 5.4.1. Overview
- 5.4.2. Testing
- 5.4.3. Logging
- 5.4.4. Supporting More Web APIs
- 5.5. Publishing
- 5.6. Team
This documentation is no longer maintained at this domain, and is now maintained at wasm-bindgen.github.io instead. Optimizing for Size with wasm-bindgen
The Rust and WebAssembly Working Group's Game of Life tutorial has an excellent section on shrinking Wasm code size, but there's a few wasm-bindgen
-specific items to mention as well!
First and foremost, wasm-bindgen
is designed to be lightweight and a "pay only for what you use" mentality. If you suspect that wasm-bindgen
is bloating your program that is a bug and we'd like to know about it! Please feel free to file an issue, even if it's a question!
What to profile
With wasm-bindgen
there's a few different files to be measuring the size of. The first of which is the output of the compiler itself, typically at target/wasm32-unknown-unknown/release/foo.wasm
. This file is not optimized for size and you should not measure it. The output of the compiler when linking with wasm-bindgen
is by design larger than it needs to be, the wasm-bindgen
CLI tool will automatically strip all unneeded functionality out of the binary.
This leaves us with two primary generated files to measure the size of:
-
Generated wasm - after running the wasm-bindgen
CLI tool you'll get a file in --out-dir
that looks like foo_bg.wasm
. This file is the final fully-finished artifact from wasm-bindgen
, and it reflects the size of the app you'll be publishing. All the optimizations mentioned in the code size tutorial will help reduce the size of this binary, so feel free to go crazy!
-
Generated JS - the other file after running wasm-bindgen
is a foo.js
file which is what's actually imported by other JS code. This file is already generated to be as small as possible (not including unneeded functionality). The JS, however, is not uglified or minified, but rather still human readable and debuggable. It's expected that you'll run an uglifier or bundler of the JS output to minimize it further in your application. If you spot a way we could reduce the output JS size further (or make it more amenable to bundler minification), please let us know!
Example
As an example, the wasm-bindgen
repository contains an example about generating small Wasm binaries and shows off how to generate a small wasm file for adding two numbers.
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