Sizzy

The product is pretty neat and feature-packed. Definitely makes frontend dev much easier, and helps spot errors in responsive builds that can be missed or too cumbersome to test

For real-time testing across various breakpoints

It has its bugs, but it is a great product. I've given only 2 stars because the Customer Support has been lacking. I've tried contacting them several times now and there's been no response. Most recently, I signed in and it says my subscription has been cancelled even though I've paid for a full year. Now, the app is a brick — an expensive one.