Shrinking your browser window isn't mobile testing. Here are 5 bugs it will never show you: 1) The button hiding under the browser bar. 100vh on iPhone Safari includes the address bar, so your "Book a call" button sits just off-screen. Use 100dvh instead. 2) The page zooms in when someone taps a form. iOS zooms into any input under 16px and stays zoomed. Set inputs to 16px. 3) The menu that only opens on hover. Phones don't have hover. The dropdown that works on desktop is invisible on touch. 4) The whole page wiggles sideways. One element 10px wider than the screen adds a horizontal scroll. Usually an image or a long URL. 5) The sticky footer that jumps over the keyboard. Fixed elements float up when the keyboard opens and cover the field the user is typing in. Most of your client's visitors are on a phone, and most of them won't report what broke. They just leave. That's why Layerdock shows your site on desktop, tablet and phone side by side, scrolling in sync. Every pin records the screen size it was left on, so "it's broken" comes with the device that broke it. Which one have you shipped by accident? I've done #1 more times than I'd like to admit.