Build a focused test matrix
Choose viewports from real audience data and business risk, not from an endless device list. Record viewport, orientation, OS profile, browser and DPR for every result.
- Around 375px for compact phones
- 390–430px for modern phones
- 768–1024px for tablets
- 1280, 1440 and 1920px for laptop and desktop
Check structure, interaction and content
A page can look correct and still fail. Test keyboard focus, touch targets, validation, dialogs, long translations, image cropping and virtual-keyboard states.
- No unexpected horizontal scrolling
- Navigation and overlays remain operable
- Forms expose labels and useful errors
- Core actions respond on slower connections
Escalate risky journeys to real devices
Viewport previews find layout issues quickly but do not replace WebKit, Chromium or a physical device. Camera, uploads, payments, sign-in, location and virtual-keyboard journeys deserve real-browser validation.
Record reproducible evidence
Log the URL, viewport, orientation, browser, steps, expected result, actual result and severity. Retest the same combination and one adjacent width after a fix.