Let's talk!Short answer
Three.js is the default when the 3D has to be custom, fast and woven into the rest of the site: it is an open source (MIT) JavaScript library that renders with WebGL and gives full control. Spline is the fastest path for a designer to publish a 3D scene without writing code, as a public URL, an embed or exported code. Unity makes sense when the web experience is really a game or a simulator, or already exists as a Unity project, and it needs WebGL 2 on desktop browsers.
The short version
- Three.js is a code library. It gives full control over rendering, interaction and performance, and lives inside your site like any other JavaScript. It needs a developer.
- Spline is a visual design tool. A designer builds and animates the scene, then publishes it as a public URL, a Viewer embed or code (Vanilla JS, React, Next.js, react-three-fiber or a Three.js loader).
- Unity is a game engine. The whole experience is built in the Unity editor and exported as a Web build. It is the natural choice for games and simulators with complex logic.
Three.js: when the 3D is part of the product
Three.js is an open source JavaScript library, under the MIT license, that draws 3D in the browser with WebGL. Because it is just code in your site, the 3D can react to scroll, share state with the rest of the page, load only what it needs and be tuned for the devices your audience uses. It fits product configurators and interactive websites where the experience and the site are one thing. The trade off: everything is built by developers, including tools a visual editor would give you out of the box.
Spline: when a designer needs to ship 3D fast
Spline is a design tool for 3D scenes with animation and events. A scene can be published as a public URL, embedded with the Spline Viewer or exported as code. Two details matter when choosing it: animations and events only carry over when exporting to Vanilla JS or React, and Spline draws with WebGPU by default and falls back to WebGL. It is a strong fit for hero scenes, product teasers and landing page moments; logic beyond its event system usually ends up needing code anyway.
Unity: when the website is really a game or a simulator
Unity is a full game engine, and its Web build runs the experience in the browser. Unity 6 supports Safari on iOS 15 or later and Chrome 58 or later on Android, and needs WebGL 2 on desktop browsers. It pays off when the experience has game logic, physics or training scenarios, or when the project already lives in Unity and also has to ship to headsets or native apps. For a marketing page it is usually more engine than the job needs.
How to choose
- If the 3D has to behave like part of the website (scroll, interface, data, text around it), start with Three.js.
- If a designer owns the scene and the interaction is simple (hover, click, states), start with Spline.
- If the experience is a game, a simulator or already exists in Unity, use the Unity Web build.
- In every case, test on the phones your audience actually uses before committing to a direction.
Sources
Frequently asked questions
- Is Three.js free for commercial projects?
- Yes. Three.js is open source under the MIT license, so it can be used in commercial projects without license fees.
- Can a Spline scene be used inside a Three.js project?
- Yes. Spline offers a Three.js loader to bring a scene into a Three.js project. Keep in mind that Spline animations and events only carry over in the Vanilla JS and React exports.
- Do Unity Web builds work on phones?
- Unity 6 lists Safari on iOS 15 or later and Chrome 58 or later on Android as supported browsers for Web builds.
- Which option is better for SEO?
- None of them makes the 3D itself readable by search engines; what ranks is the HTML text around it. Three.js and Spline embeds sit inside a normal page, so that text is easy to keep. With a Unity build, plan the surrounding page just as carefully.
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