Pixel Density
What pixel density means, how it affects screenshot resolution, and common confusion with DPI.
Pixel density is the number of physical pixels per unit of length on a display, measured in pixels per inch (PPI). It depends on the screen's resolution and its physical size. A 27-inch display with 5120×2880 pixels has a diagonal of about 5,874 pixels, which gives roughly 218 PPI.
Higher density makes text and lines look smoother at the same viewing distance. To keep interface elements a usable size, operating systems scale them. macOS measures the interface in points and renders each point with 1×1 pixels on a standard display or 2×2 pixels on a Retina display.
On the web, the same ratio is called the device pixel ratio: the number of physical pixels per CSS pixel.
Pixel density and display sharpness
Two displays with the same resolution but different sizes have different densities. A 1920×1080 panel looks sharp at 13 inches and coarse at 27 inches. Density alone does not determine what you see: viewing distance and scaling settings also matter.
How pixel density affects screenshots
Screenshots record physical pixels. On a 2x Retina display, a capture area of 1600×900 points produces a 3200×1800 pixel image. The same area on a 1x external monitor produces 1600×900 pixels. If a capture session moves between displays, image sizes in the set change.
Temposhot shows a Display Configuration Changed dialog when the display setup changes during capture, with Continue with Selected Display or Stop Capture.
Device pixel ratio
| Device pixel ratio | Example | 400 CSS px wide element |
|---|---|---|
| 1 | Standard desktop monitor | 400 pixels |
| 2 | Mac Retina display | 800 pixels |
| 3 | Many current phones | 1200 pixels |
Browser tools and screenshot libraries let you set the device pixel ratio, so a desktop can produce phone-density captures.
Common mistakes
- Mixing 1x and 2x screenshots in one document, so some look blurry or oversized.
- Confusing PPI of a display with the DPI field stored in an image.
- Displaying 2x screenshots at their full pixel size on a web page.
- Downscaling 2x captures by an odd factor instead of exactly 50 percent.
Taking the same screenshots again and again?
Run every capture on the same display so image sizes stay consistent. See screenshot automation on Mac.
Common questions
How do I check a screenshot's pixel size?
Open it in Screenshot Resolution Checker, or use Preview's inspector on a Mac.
Is pixel density the same as resolution?
No. Resolution is the pixel count. Density is pixels per inch of physical screen.
Sources
Related resources
- Capture controls and recovery: display changes during capture.
- DPI: the print-oriented resolution value.
Taking the same screenshots again and again?
Temposhot captures a screen, window or area on a timer and exports the set as a PDF, images, ZIP or MP4. The free browser tools fix single images.
Related resources
Related terms
- DPIWhat DPI means for screenshots, how it affects resolution and file size, and common confusion with PPI.
- Retina ScreenshotWhat a Retina screenshot is, why it's 2x the expected size, and how to handle high-DPI captures.
- Screenshot ResolutionA screenshot copies the pixels on screen, so it doesn't lower quality by itself. See what makes screenshots blurry and what decides their size in MB.
- Image ResizeWhat image resizing is, how it differs from cropping, and mistakes to avoid when scaling screenshots.
- Viewport ScreenshotWhat a viewport screenshot is, how it differs from full-page capture, and when it's the right choice.