FAQ

What is Window.js?

Window.js is a Javascript runtime with access to desktop windowing, input, file and graphics APIs.

What does Window.js build on?

  • The Javascript engine is v8.
  • Platform integration for windowing and input is built on GLFW.
  • The canvas API is largely built on the Skia graphics library.
  • Access to native graphics is performed via the EGL and OpenGL ES 3.0 APIs provided by ANGLE. Windows uses the Direct3D 11 backend; macOS and Linux use desktop GL.
  • Subprocesses and IPC is built on libuv.
  • Window.js itself is mostly written in C++17. The build system is CMake.
  • The documentation is built with Jekyll for its integration with Github Pages.

Is Window.js compatible with web APIs?

Full compatibility with web APIs is not a goal of Window.js.

However, Window.js programs can benefit from the large number of useful libraries written for Node.js and for the web. The web APIs are also extensively documented and widely known.

Window.js tries to follow web APIs by default, and offers more convenient or performant APIs where it makes sense.

For example, the canvas API mostly follows the web canvas API, and the canvas documentation at MDN applies to Window.js as well.

On the other hand, the file API is custom to Window.js. Is it more straightforward and efficient for the expected use cases of Window.js. The equivalent web APIs are either non-existent, or more cumbersome to use due to web security requirements that Window.js doesn’t observe.

A longer-term goal is to support the three.js 3D programming library in Window.js, which will require extensive compatibility with web APIs.

Is Window.js stable?

Window.js is implemented to be stable at runtime: memory shouldn’t leak, misuse of APIs shouldn’t cause crashes, and the Window.js runtime should never deadlock.

The APIs exposed by Window.js are not stable at this time. The current APIs are at a very early stage in their design and will evolve if simpler and more performant designs make sense.

API stability is a longer-term goal.

Is Window.js secure?

Window.js does not implement the security features that are common in web browsers. It does not sandbox the Javascript code, and it exposes full access to the filesystem as a native program would have.

Given that, Window.js should not misbehave in unexpected ways and doesn’t read or write any files or other metadata in the system, like the registry on Windows, other than via the exposed APIs.

Is Window.js performant?

Window.js bundles the v8 Javascript engine, and performance of Window.js programs is comparable to other Javascript programs built on v8 such as Chrome, Node.js and Electron.

The expected performance should be good enough for interactive 2D graphics programming and for exploratory 3D programming, but proper benchmarking hasn’t been done yet.

Javascript is a garbage collected language, and high frame-rate programs may see frame drops due to GC pauses if they make several allocations per frame.

Programs that need the highest performance (such as numerical computing, AI model training and similar) won’t reach the performance that native code can achieve.

Does Window.js support WebGL?

Not yet. Supporting the WebGL 2 API is a goal.

Does Window.js support sound and audio?

Not yet. Introducing a sound API is a goal.

Does Window.js support networking?

Not yet. Supporting the fetch API and sockets (UDP, TCP, Websockets) is a goal.

Does Window.js support mobile platforms?

No, and that is not a goal of the project.

Does Window.js support autoupdates?

No, though that could be eventually implemented by the application code.

Does Window.js support crash reporting?

No, though that could be eventually supported via a crash handling API.

Does Window.js support Typescript?

Typescript is not integrated into Window.js yet.

In the short-term, Window.js should provide Typescript typing declarations for its APIs.

Longer-term, Window.js could integrate with the Typescript compiler to support reloading with F5 and showing any Typescript compilation errors directly in the main window.

Does Window.js install any files?

No. Window.js is distributed as a single, statically-linked binary and doesn’t make any modifications to the host computer: no files are written, read or modified, no keys are edited in the Windows registry, etc.

Window.js has no telemetry and doesn’t open any network connections.

The applications built on Window.js have access to the local filesystem APIs (and, eventually, to networking). Their usage of those APIs is outside the scope of Window.js.

What kind of programs can be built on Window.js?

  • 2D and 3D exploratory programs, using the 2D canvas and WebGL APIs.
  • Interactive 2D applications like Scratch and Processing.
  • Cross-platform 2D games for desktop platforms.
  • Experimenting with 2D algorithms for layout engines, widget libraries, etc.
  • A toy web browser and HTML renderer, as a learning exercise.

What kind of programs should not be built on Window.js?

  • Security. Window.js has no protections against malicious third-party code and shouldn’t be used as a generic runtime for untrusted code.
  • Highest performance. Javascript is compiled just-in-time, has a garbage-collected managed heap and is single threaded.
  • Text-heavy programs. Window.js doesn’t do any text layout and doesn’t have any text editing widgets (though such a library could be built).
  • A generic web browser to be distributed to end users.

How does Window.js compare to a web browser?

  • Window.js doesn’t support HTML nor CSS, and doesn’t have a DOM.
  • Window.js doesn’t have browser components like the URL bar, tabs, or menus.
  • Window.js gives full control of the native window to the application.
  • Window.js has no security: no same-origin policy, no sandbox, no protections against malicious code. Window.js programs have unrestricted access to the filesystem.
  • Window.js has more convenient APIs for desktop applications.
  • Window.js doesn’t have the tooling that supports web development, like the DOM inspector. It has a very simplistic console for development.

How does Window.js compare to Node.js?

  • Window.js and Node.js are very similar. Whereas Node.js was designed to build web servers and command-line tools, Window.js was designed to build 2D applications.
  • Node.js was built before Promises and async/await, and its APIs rely heavily on callbacks. Window.js APIs use Promises.
  • Window.js is a smaller binary and has less dependencies than Node.js.
  • Window.js does not support NPM or node_modules.
  • Window.js doesn’t use node modules nor require(). Window.js supports ES6 modules and async import().
  • Window.js does not support headless programs yet. This is planned for subprocesses, and Window.js programs can run with an invisible window.
  • Window.js doesn’t have a large community nor wide documentation and plugins as Node.js does.

How does Window.js compare to Electron?

  • Electron is a mature product that has been deployed widely. Window.js is an untested and recent open-source program.
  • Electron has very rich APIs for building web pages, widgets, text layout, and everything else offered by modern web APIs. Window.js doesn’t have any of those tools or APIs.
  • Window.js is a smaller binary with less dependencies than Electron.
  • Window.js applications run in a single process. The Javascript code for the UI and any other operations runs in the same thread. I/O and other blocking APIs internally use worker threads and pass the results back to Javascript using Promises. Window.js supports subprocesses.
  • Window.js doesn’t have the development tooling that Electron offers like the DOM inspector, CSS editor, etc.
  • Window.js doesn’t have a large community nor wide documentation and plugins as Electron does.

How does Window.js compare to Processing and p5.js?

Window.js could be a great way to execute Processing programs on the desktop, by porting p5.js.

Window.js aligns well with the goals of Processing and p5.js: make graphics programming more accessible and easier to learn.

Processing has better documentation and many examples on the web, and a large community.

Window.js provides a better way to bundle the app as a standalone application, and has more APIs for desktop integration.

There is experimental support to run p5.js scripts in Window.js.

Does Window.js run on Windows Subsystem for Linux (WSL)?

Yes! Use an X server like VcXsrv and make sure to have Mesa version 23 or later installed, to support GLES3.

When using VcXsrv, disable Native opengl and don’t set LIBGL_ALWAYS_INDIRECT.