Spline

Use Spline only when the design genuinely needs a live, interactive 3D scene the user can drag or that reacts to scroll — for a fixed camera path, an exported MP4 or a Lottie file is smaller and faster. You cannot author a scene programmatically: a human builds it in the editor and hands you a scene URL, after which your job is the <spline-viewer> tag or the @splinetool/runtime React wrapper plus a lazy-load boundary, because these bundles are heavy. The marketing site is a JS-rendered shell and the editor is login-walled, so do not expect to scrape scene data or docs content without a session.

Why it is here. It is the tool that made real-time 3D on the web a normal product decision instead of a WebGL engineering project. The trade-off it hides is weight — a Spline hero routinely costs more than the rest of the page.