I think you have a different idea of what gpu acceleration means here. When we say that animating transform and opacity is fast, it means that we can animate it without rasterizing content over and over again i.e. only use composition. This is independent of how rasterization takes place. Rasterization itself can be gpu accelerated, Chrome has started doing this on mobile[1].<p>Animating other CSS properties such as font-size require us to rasterize new content on every frame of animation. That is the inherent reason for why it&#x27;s slow. Again we can use the GPU for rasterization but we&#x27;re still going to do it every frame instead of caching the result in a texture that&#x27;s then composited over and over again.<p>[1]: <a href="https:&#x2F;&#x2F;www.chromium.org&#x2F;developers&#x2F;design-documents&#x2F;chromium-graphics&#x2F;how-to-get-gpu-rasterization" rel="nofollow">https:&#x2F;&#x2F;www.chromium.org&#x2F;developers&#x2F;design-documents&#x2F;chromiu...</a>