The 'Confirm Payment' button in the IndiGo mobile booking flow was 32px tall. Apple's HIG says 44px minimum. Google's Material says 48dp. We knew this. We had it in our design system.
What happened: a developer used the desktop component on mobile without adjustment. Passed QA on a Pixel 6 (large screen, easy tap). Failed silently on smaller devices and users with less precise thumb movements.
Hotjar session recordings showed the pattern: users would tap, nothing happened, they'd tap again, sometimes hitting 'Back' by mistake. 34,000 failed tap events per day. On the payment confirmation step.
Six months of this before someone noticed the session recording pattern and connected it to the button size.
What it cost: conservative estimate of 2-3% payment abandonment attributable to the tap target, across 6 months of mobile bookings. The math gets uncomfortable quickly.
Accessibility standards aren't just for accessibility. A 44px tap target is a conversion target. Test on the smallest screen your users actually use.
