Screen Sizes & Viewport Cheat Sheet for 2026

Every responsive bug report starts the same way: "it looks broken on my phone." Then you spend ten minutes hunting for that phone's viewport width — one site lists the panel resolution, another lists a viewport from two generations ago, and a third just says "various."

This is the cheat sheet I keep coming back to: the device viewports worth testing in 2026, the framework breakpoints next to them, and the three numbers — resolution, viewport, DPR — that developers constantly mix up. All values below are portrait CSS-pixel references. Treat heights as references, not guarantees: mobile browser bars, keyboards and zoom change the visible height, while width stays comparatively stable.

Phone viewports worth testing

Eleven models cover nearly every width your layout will meet in production, from the narrow 360px Android baseline to the 440px Pro Max class.…