How to use the What Is My Screen Resolution
- Open the page — the values appear immediately.
- Resize the window or rotate your phone to see the viewport change.
- Copy the details to share them in a bug report.
Screen resolution vs viewport
- Screen resolution is the size of the whole display in CSS pixels (
screen.width × screen.height). - Viewport is the area of the browser window available to the page (
innerWidth × innerHeight); this is what CSS media queries use. - Device pixel ratio (DPR) is the number of physical pixels per CSS pixel. A phone with DPR 3 and a 390-pixel-wide viewport actually has 1170 physical pixels across.
Common screen sizes
| Device type | CSS viewport | DPR |
|---|---|---|
| Modern iPhone | 390–430 × 844–932 | 3 |
| Android phone | 360–412 × 780–915 | 2.6–3.5 |
| iPad | 768–1032 × 1024–1376 | 2 |
| Laptop | 1280–1536 × 720–960 | 1–2 |
| Full HD monitor | 1920 × 1080 | 1 |
| 4K monitor (scaled) | 1920–2560 × 1080–1440 | 1.5–2 |
Why the numbers look “wrong”
Operating systems scale the display: a 4K screen at 150 % scaling reports 2560 × 1440 CSS pixels with DPR 1.5. Browser zoom changes the DPR too — zoom to 200 % and the viewport halves. That is expected behaviour, not an error.
For developers
Design with CSS pixels and test the common viewport widths (360, 390, 768, 1024, 1280, 1536). Serve sharp images to high-DPR screens with srcset and resize them with the image resizer. Fluid typography with the clamp() calculator avoids breakpoints for font sizes altogether.
Tools that pair well with the What Is My Screen Resolution
- What Is My IP — Your public IP address and everything your browser reveals to the websites you visit — user agent, screen, language, timezone and request headers.
- User Agent Parser — Decode any User-Agent string into browser, engine, operating system and device — and find out whether it belongs to a search engine, AI crawler or script.
- Aspect Ratio Calculator — Resize images and videos without distortion: fill in a ratio and one side to get the other, or enter a size to find its ratio — with ready-to-paste CSS.
- PX to REM Converter — Convert between pixels, rem and em with your own root font size — or paste a whole stylesheet and convert every px value in one go.
Frequently asked questions
Why does my 4K monitor show a smaller resolution?
Display scaling: Windows and macOS enlarge everything, so the browser reports the scaled size in CSS pixels. Multiply by the device pixel ratio for the physical resolution.
What is the difference between screen size and viewport?
The viewport excludes the browser’s toolbars, tabs and window borders — it is the space the web page actually gets.
Is this information sent anywhere?
No. It is read by your browser and shown on this page only.