Low-FPS Spinners

The page cites a reduction from ~50% to ~3-8% GPU usage on a typical laptop (i7-7500U). Per-design Chromium measurements include a rotating segmented ring at 6-10% (HTML) / 8-9% (SVG) at 10 steps/s, and a fade-in-place segmented ring at 14% (HTML) / 8-9% (SVG) at 10 steps/s and 30% (HTML) / 13-15% (SVG) at 30 steps/s.

No. The spinners are CSS-only (with HTML or SVG markup), and the showcase page itself uses no JavaScript at all.

Yes — the code is public domain, so you can copy it as you like.

The page recommends SVG in general: rotating HTML spinners visibly wobble at small sizes, and designs that animate many separate elements are cheaper in SVG because HTML gives each animated element its own GPU layer while SVG redraws a single layer.

You likely have "reduced motion" enabled in your desktop settings; the page respects that setting and displays the spinners still.

Using Chromium's Task Manager (Shift+Esc on Linux/Windows), looking at the "GPU Process" row on the i7-7500U laptop, with one design shown at a time. Verdicts not marked "measured" are derived expectations based on how each design animates.