Guides
Plain-English explainers written and reviewed by the Screen Size Checker team. No jargon, no filler.
The screen sizes that actually matter in 2026
Forget the 50-row resolution charts. A handful of sizes cover most of the web’s traffic — here they are, and how to think about the rest.
5 min read · Reviewed July 2026
Device pixel ratio: why your 4K phone reports 390 pixels
Physical pixels, CSS pixels, and the 2×/3× multiplier between them — the concept that explains most "why is my image blurry" mysteries.
5 min read · Reviewed July 2026
Viewport vs screen resolution: the difference that breaks layouts
Your screen is 1920 wide but your website gets 1050. Where the pixels go, and why designing to "screen sizes" is subtly wrong.
4 min read · Reviewed July 2026
How to choose responsive breakpoints (without cargo-culting)
768 and 1024 are fossils of the 2010 iPad. Let content decide where your layout bends, with a sane default set if you must have numbers.
5 min read · Reviewed July 2026
PPI, retina, and when sharpness stops mattering
Pixel density decides whether you can see the pixels. The math, the marketing, and the point past which your eyes can’t tell.
4 min read · Reviewed July 2026