JSAR (/dʒ:-sar/) is a Web browser engine designed for the spatial Web. It enables you to create and present immersive Web contents using the modern Web technologies (HTML5, CSS3, TypeScript) and seamlessly integrate them into mainstream 3D engines like Unity, UnrealEngine, and other 3D engines.

To understand the architectural decisions and core concepts behind JSAR, read our comprehensive guide: Understanding the Spatial Web Browser Engine.

Spatial Web

The Spatial Web represents the next evolution of the Web, where every HTML element exists in three-dimensional space with real 3D coordinates, rather than being confined to flat 2D screens. This spatial transformation enables developers to freely leverage Web technologies to create truly immersive experiences, seamlessly blending virtual reality (VR), augmented reality (AR), and mixed reality (MR) into both our physical world and any digital virtual environments.

Key characteristics of the Spatial Web include:

3D-First Design: Content and interfaces are designed to exist in 3D space
Natural Interaction: Users can interact with digital content using natural gestures and movements
Contextual Awareness: Digital experiences that understand and respond to their physical surroundings
Persistent: Digital content can remain anchored in physical space across sessions

Key Features

Designed for the spatial Web - Every HTML element (including 2D & 3D) is spatially rendered in the browser.
Web Standards Compliant - Supports modern Web standards, including HTML5, CSS3, DOM, WebGL, WebXR and others.
High Performance - Dynamically batches all spatialized HTML elements into ≤10 GPU draw calls per frame.
Cross-Platform - Delivers flawless performance across every platform (desktop, mobile, and XR) with pixel-perfect consistency.
Web Developer Friendly - Deep Chrome DevTools integration for seamless debugging and profiling.

Web Compatibility Overview

Supported URL Formats to Request

Like the classic Web browser, it supports not only the HTML document, but also lots of formats, such as SVG, 3D models, etc. The following formats is expected to support:

Format	Status	Recommended Use Case
HTML	Partially	Browsing classic Web pages
GLTF	OK	Displaying 3D models
JPEG/PNG	OK	Displaying images
SVG	OK	Displaying SVG images

Scripting & Modules

API	Status	Test Suite
JavaScript	Ok	-
TypeScript	Ok	-
ECMAScript Module	Ok	-
WebAssembly	Ok	-
Web Worker	Ok	-

3D Graphics

API	Status	Test Suite
WebGL1	Ok	https://github.com/KhronosGroup/WebGL/tree/main/sdk/tests/conformance
WebGL2	Ok	https://github.com/KhronosGroup/WebGL/tree/main/sdk/tests/conformance2
WebGPU	Not started	https://github.com/gpuweb/cts

Rendering Backends

The following are supported renderer backends:

Backend	OS	Status	Test Suite
OpenGLES3	Android	Ok	-
OpenGL	macOS	Partially	-
Metal	macOS	Not started	-
D3D11	Windows	Not started	-

WebXR Device APIs

API	Status	Test Suite
Spaces and Reference Spaces	Ok	-
Stereo Rendering	Ok	-
Inputs and Input Sources	Ok	-

Supported Input Sources

Input Source	Status	Target Ray Mode	Gamepad	Profiles
gaze	Ok	gaze	No	-
hand(2)	Ok	tracked-pointer	No	-
main controller	Ok	tracked-pointer/screen	Yes	-
transient	Not implemented	transient-pointer	No	-

Note: Gamepad is not supported in the current version.

Features

Feature	Status	Test Suite
Hit Test	Not implemented	-
Anchors	Not implemented	-
Hand Tracking	Ok	-
Eye Tracking	Not implemented	-
Depth Sensing	Not implemented	-
Face Tracking	Not implemented	-
Body Tracking	Not implemented	-
Environment Probes	Not implemented	-
Light Estimation	Not implemented	-

Multimedia APIs

In Web multimedia, there are the following APIs that JSAR would support:

Playback: play audio and video, and use Web Audio API to create audio effects.
Capture: capture audio and video from the device.

Playback

API	Status	Test Suite
`HTMLAudioElement`	Ok	-
`HTMLVideoElement`	Not started	-
Web Audio API	Not started	-

Capture

API	Status	Test Suite
`MediaDevices`	Not started	-
`MediaRecorder`	Not started	-

Canvas

API	Status	Test Suite
`RenderingContext2D`	Ok	-
`PDFRenderingContext`	Not started	-
`HTMLRenderingContext`	Not started	-

Note: PDFRenderingContext and HTMLRenderingContext are introduced by JSAR, which is used to customize the PDF and HTML rendering.

Classic Rendering

API	Status	Test Suite
DOM API	Partially	-
HTML5	Partially	-
CSS3	Partially	-
Web Component	Not started	-

Contributing

To contribute to the project, you need to follow the steps below to build this project from source.

Prerequisites

$ node -v
v18.16.1

$ rustc -v
rustc 1.86.0-nightly (243d2ca4d 2025-01-06)

Note that JSAR requires Rust nightly toolchain to build.

Depending on your target platform, you'll need to add the corresponding Rust targets:

For macOS builds:

$ rustup target add aarch64-apple-darwin
$ rustup target add x86_64-apple-darwin

For Android builds:

$ rustup target add aarch64-linux-android

Build from source

Firstly, you need to install the dependencies and build the JSAR JavaScript bundle which is used in the runtime.

$ npm install && make jsbundle

Then you can build the runtime library:

$ make darwin    # for macOS universal library
$ make android   # for Android-aarch64 library

If you want to do a clean build, you can run:

$ make darwin CLEAN=yes

Supported parameters:

CLEAN: Clean the build directory before building.
RELEASE: Build the release version of the library.
INSPECTOR: Enable the inspector.

Loaders

The loaders are more convenient way to integrate JSAR into your applications, the following loaders are planned to be developed:

Loader	Status	Description
jsar-loader-unity	Ok	Integrates JSAR into Unity applications
jsar-loader-unreal	Not started	Integrates JSAR into Unreal Engine applications

To develop a new loader, you could see the Embedder API Documentation for more details.

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