feature: box-shadow status: caution tags: prefixes kind: css polyfillurls:
box-shadow is safe to use most of the time, except when you are applying it on a large area as that may cause significant performance impact when interacting with the page (on scroll and hovers, but also transitions and animations).
Polyfills are unnecessary for box-shadow. They are too costly and slow down page load. Users without a modern browser will not see a shadow, but aren't checking your site in multiple browsers anyhow.
Box shadows can also be applied safely without prefixes.