Checklist: QA-ing responsive breakpoints before a builder page goes live

Checklist: QA-ing responsive breakpoints before a builder page goes live

The builder's preview lies — test on real widths.
— Check the three default breakpoints, then add the gaps: 360px (small phones) and ~820px (tablet portrait), where layouts usually snap.
— Verify font sizes use fluid clamp/responsive units, not fixed per-breakpoint values you'll forget to update.
— Hunt for horizontal scroll: a single full-width element overflowing is the classic culprit.
— Test tap targets at 44px minimum; builder buttons often shrink below it on mobile.
— Confirm hidden-on-mobile elements aren't still loading (display:none still downloads images).

Pros:
— Catches the breakpoints the builder doesn't show by default.
— Prevents the most common mobile bug reports.

Cons:
— Manual; emulators miss real-device quirks.

Best for: any page before launch, especially template-driven layouts reused at scale.