Build 3D, music and physics for the web. By hand or with AI.

Your project runs in the browser. You write JavaScript in Code components, or let an AI write it for you. Building and previewing are free.

New: Make music in R3 — the Sound Studio shapes sounds from layers you can hear as you go, and the Song Studio arranges them into a song on a timeline. Open the Song Studio · How a track was made with Claude · Hear the track

Three ways to build.

• Build it yourself. Free, no AI. Open the editor, add objects, and write JavaScript in a Code component. It runs every frame, or when a key, a click or a collision happens. Start with the Quick start · Hello world, by hand
• Use your own AI. Free with your own Claude. Connect Claude (claude.ai, Claude Code, or Claude in R3's browser terminal). You sign in with R3, with no key to copy. Your AI builds, runs and checks the project while you watch. Connect your AI
• R3 Builder. We run the AI. Paid with R3 credits. Describe a scene or a model in plain words, and R3 Builder builds it in your project. You need no AI account, and you pay only for what it uses. How R3 Builder works

For programmers.

A project is your program. A Code component on RENDER_BEFORE is your main loop. Events (KEY_DOWN, MOUSE_CLICK, PHYSICS_COLLISION) are your interrupts. A component is a struct with live fields, and its entityRef is the variable name. Assets are your files: images, sounds, models. The language is JavaScript, in the browser, with nothing to install.

R3 for programmers

What you can make with R3

• 3D scenes and games. Build a scene from components (meshes, lights, cameras, terrain, materials and textures) in the editor, then make it do things with code: write it yourself, or ask Claude to write it.
• Physics. Rapier physics in the browser: rigid bodies, colliders, joints, raycast vehicles and terrain, on the same canvas as the graphics.
• Music and sound. The Sound Studio shapes sounds from layers you hear as you go; the Song Studio arranges tracks and clips into a song on a timeline. Patterns, drum grids and samples play in the scene, and every beat is an event your code can react to.
• Blender models. Open a .blend file in the browser with its materials and textures, then use its parts in your projects. Open the Blender viewer, no account needed.
• Build with AI. Claude in R3's browser terminal is already connected to your account; claude.ai and Claude Code connect through R3's MCP server, no key needed. Or describe it to R3 Builder, which builds it in your project for you, paid with R3 credits.
• Preview and publish. Share a private preview link for 7 days for free. Publishing makes a live page at your own address on live.r3js.org that you can embed anywhere, and you can roll back to an earlier release at any time. Going live comes with a plan.

Everything runs in the browser: nothing to install. Every part of a project is a component you can see and change in the Inspector, and the code is real JavaScript you can read and edit.

Start here

• Quick start: from a new account to a shared link in five steps.
• Tutorials: step-by-step guides that open beside the editor, from your first scene to physics, sound and code.
• Examples built with Claude: a neon maze game, a helicopter shooter and a psy techno track, each prompt by prompt.
• Showcase: projects people made and published with R3. Open one and play it in your browser.
• Videos and how-to videos: short clips of R3 in real use, with transcripts.
• Documentation and the API reference: every component, system and event.
• Roadmap: what is being built next. Vote for what you want.

Free to build by hand. AI is optional. No cookie banner. No ads.