CSS Supports Directives
Feature detection using Modernizr is a client-side best practice. Still, you can also use the CSS @supports rule, which is a conditional group rule that can test whether the browser supports features and if not can degrade gracefully.
The code example below, checks if the browser supports 'flexbox'. If it is then the page body background colour will be red.
This short blog shows you have you can use the @supports feature of CSS.
I hope you find it useful and if you have any comments, please use the form below.