Depends on how critical it is for you/your company. I work on products that have internal tooling, and if they run on the latest version of Chrome, it's good en

Depends on how critical it is for you/your company. I work on products that have internal tooling, and if they run on the latest version of Chrome, it's good enough (although I personally test them on Firefox, too, and someone used an older version of Safari the other day, and found a weird bug). However, some of our tools are used by the general public (I've found the user agent for a coupon app as well as some PlayStation browser in the logs; might have been spoofed, of course). Those are written to the lowest common HTML/CSS/JS standards, so we don't try fancy features, and Babel or similar can be helpful. IE11 is out of grace, but we still support years old versions of most browsers, because it costs money and goodwill when too many fail.