The wasm-bindgen Command Line Interface

The wasm-bindgen command line tool has a number of options available to it to tweak the JavaScript that is generated. The most up-to-date set of flags can always be listed via wasm-bindgen --help.


cargo install -f wasm-bindgen-cli


wasm-bindgen [options] ./target/wasm32-unknown-unknown/release/crate.wasm


--out-dir DIR

The target directory to emit the JavaScript bindings, TypeScript definitions, processed .wasm binary, etc...


This flag indicates what flavor of output what wasm-bindgen should generate. For example it could generate code to be loaded in a bundler like Webpack, a native web page, or Node.js. For a full list of options to pass this flag, see the section on deployment

--no-modules-global VAR

When --target no-modules is used this flag can indicate what the name of the global to assign generated bindings to.

For more information about this see the section on deployment


Output a TypeScript declaration file for the generated JavaScript bindings. This is on by default.


By default, a *.d.ts TypeScript declaration file is generated for the generated JavaScript bindings, but this flag will disable that.


When the module attribute is used with the wasm-bindgen macro, the code generator will emit corresponding import or require statements in the header section of the generated javascript. This flag causes those import statements to be omitted. This is necessary for some use cases, such as generating javascript which is intended to be used with Electron (with node integration disabled), where the imports are instead handled through a separate preload script.


Generates a bit more JS and wasm in "debug mode" to help catch programmer errors, but this output isn't intended to be shipped to production.


When post-processing the .wasm binary, do not demangle Rust symbols in the "names" custom section.


When post-processing the .wasm binary, do not strip DWARF debug info custom sections.


When generating bundler-compatible code (see the section on deployment) this indicates that the bundled code is always intended to go into a browser so a few checks for Node.js can be elided.


Enables usage of the TC39 Weak References proposal, ensuring that all Rust memory is eventually deallocated regardless of whether you're calling free or not. This is off-by-default while we're waiting for support to percolate into all major browsers. For more information see the documentation about weak references.


Enables usage of the WebAssembly References Types proposal proposal, meaning that the WebAssembly binary will use externref when importing and exporting functions that work with JsValue. For more information see the documentation about reference types.


Don't add WebAssembly fallback imports in generated JavaScript.