#wasm #web


Manages the building of WebAssembly single page app frontends from a build.rs script so that they can easily be embedded into Rust API projects

5 releases

0.1.4 Feb 17, 2021
0.1.3 Feb 8, 2021
0.1.2 Jan 6, 2021
0.1.1 Jan 5, 2021
0.1.0 Jan 5, 2021

#381 in Web programming

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Web Bundler

crates.io build status

Manages the building of WebAssembly single page app frontends from a build.rs script so that they can easily be embedded into Rust API projects.

Internally, the bundler uses wasm-pack to do the actual webassembly compilation.


From a clean Rustup-based Rust installation, there are no additional steps. Web Bundler will download and install any dependencies it needs.

For Rust installations that are not done with Rustup, you will need to add the wasm32-unknown-unknown compilation target manually (see the wasm-pack docs for details on how to do this).

Running the Demo Example

There is an example usage in the example directory. To run the example, open a terminal in the example directory and run cargo run. Then, open a web browser and navigate to http://localhost:3030/. You should see a Seed web application.


Web-bundler expects you to have two projects: a frontend project using a single page app framework (like Seed), and a backend project using a web server framework (like warp). These projects should be in a common workspace.

Changes to your frontend project

  1. Update your index.html to allow templating in Javascript and CSS.

    Specifically, you need to add {{ stylesheet | safe }} to the <head> section, and {{ javascript | safe }} to the end of the <body>. Optionally, if you want to set the base url, add <base href="{{ base_url }}"> to the <head> as well.

    See the example frontend index.html.

  2. Create a root stylesheet for your app called ./css/style.scss.

    This stylesheet will be compiled to CSS, and embedded directly into your index.html file.

    See the example frontend style.scss.

  3. Put all of your static assets in the static directory

    All files in the static directory will be copied directly to a static folder in the output directory.

    See the example frontend static directory.

Changes to your API project

  1. Update your Cargo.toml to depend on your frontend project and web-bundler

    We depend on the frontend project in Cargo.toml so that Cargo knows to rerun build.rs whenever the frontend project changes.

    See the example backend Cargo.toml.

  2. Add a build.rs script that calls web-bundler for your frontend

    See the example backend build.rs.

  3. Use Rust Embed to embed your built frontend into your API binary

    See the example backend main.rs. Our example uses the warp web server. Rust Embed also has examples for other web servers in their repo.

target and web-target directories

When web-bundler compiles the frontend, it overrides the default target directory to be web-target instead of target. This is done because, if the backend and frontend are in the same workspace, Cargo will already be locking target while running the build.rs script.


Licensed under either of

at your option.


~1M SLoC