They use a polyfill for Firefox on Youtube because of a never-standardised feature too: https://twitter.com/cpeterso/status/1021649116391075840 https://twitter.

They use a polyfill for Firefox on Youtube because of a never-standardised feature too: https://twitter.com/cpeterso/status/1021649116391075840 https://twitter.com/cpeterso/status/1021649116391075840