Screen resolution vs. browser window size
Screen resolution is the number of physical pixels on the display, such as 1920 × 1080 on a Full HD laptop or 1440 × 3120 on a Galaxy S25 Ultra. CSS pixels (the screen size websites see) are larger, because phones and high-resolution laptops scale everything up so text stays readable. The device pixel ratio is how many physical pixels make up one CSS pixel. Physical resolution = CSS size × pixel ratio.
Why the resolution may look lower than advertised
- Display scaling: Windows set to 125% or 150% makes websites see fewer CSS pixels. The physical resolution line on this page accounts for that.
- Phone resolution settings: Samsung Galaxy phones often run at FHD+ by default to save battery. Change it in Settings › Display › Screen resolution.
- Browser zoom: zooming in or out changes the pixel ratio. Press Ctrl + 0 (⌘ + 0 on Mac) to reset zoom before measuring.
- External monitors: the browser reports the screen the window is on. Move the window to measure another monitor.
Common screen resolutions
- HD: 1280 × 720 · Full HD (1080p): 1920 × 1080 · QHD (1440p): 2560 × 1440 · 4K UHD: 3840 × 2160
- MacBook Air 13" (M-series): 2560 × 1664 · MacBook Pro 14": 3024 × 1964
- iPhone 16: 1179 × 2556 · iPhone 16 Pro Max: 1320 × 2868
Want to check the display itself? Try the dead pixel test, the refresh rate test, or the full phone or laptop diagnostic.
Frequently asked questions
How do I find my screen resolution?
This page shows it instantly. On Windows you can also open Settings › System › Display › Display resolution, on a Mac System Settings › Displays, and on Samsung phones Settings › Display › Screen resolution.
Why is my screen resolution different from my browser size?
Phones and high-resolution laptops scale the screen so text isn’t tiny. Websites see CSS pixels, and each CSS pixel is made of several physical pixels. The device pixel ratio tells you how many.
What is device pixel ratio?
It is the number of physical pixels per CSS pixel in each direction. A ratio of 3 means a 412 × 915 CSS screen has 1236 × 2745 physical pixels. Browser zoom and display scaling change it.