Screen Resolution Test: Check Your Display Size and Scaling
See your screen resolution, the real pixel count behind it, your browser viewport and scaling, updated live as you resize.
Your viewport inside your screen, to scale
Display details
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Resize the window, rotate your device, change browser zoom or move the window to another monitor. Every value updates instantly.
“What is my screen resolution?” sounds like a question with one answer, but a modern computer actually juggles several. There is the number of physical pixels on the panel, the resolution your operating system reports after scaling, and the smaller area your browser gets to draw in. Mixing them up is why a 4K laptop can report 1536 x 864, why a website looks blurry on one monitor and sharp on another, and why screenshots come out a different size than you expected.
This screen resolution test shows all of them together: screen size, physical pixels, browser viewport, device pixel ratio, aspect ratio and a named standard such as Full HD or QHD. A to-scale diagram shows where your browser window sits on the screen, and everything updates live as you resize, zoom or move between monitors.
How to check your screen resolution
- Open this page. The four headline values appear instantly, no button needed.
- Read the name under Display details, such as Full HD (1080p) or 1080p at 125% scaling.
- Drag the window edges, rotate your phone or change browser zoom and watch the numbers update.
- Press Check in fullscreen to see the viewport grow to the full screen size.
- Use Copy details to paste every value into a support ticket, forum post or bug report.
The numbers explained
Screen resolution (CSS pixels)
This is the size your operating system tells the browser the screen is, after display scaling. On a 1920 x 1080 monitor at 100 percent scaling it matches the panel exactly. On a laptop with a 2880 x 1800 panel set to 200 percent scaling, it reports 1440 x 900, because each layout pixel is drawn with four real pixels.
Physical pixels
The tool multiplies the reported screen size by the device pixel ratio to estimate how many real pixels the panel has. This is the resolution printed on the box and the one that matters for sharpness. It is an estimate because some systems round scaled values, so a result one or two pixels off the spec is normal.
Device pixel ratio and scaling
Device pixel ratio, shown as a percentage, is your scaling. 1.0 means 100 percent, 1.25 means 125 percent, 2.0 means the Retina style 200 percent. Browser zoom changes it too: zoom to 150 percent and the ratio rises, which is why zooming makes the viewport smaller in CSS pixels.
Viewport
The viewport is the area inside the browser window where a page is drawn, excluding toolbars, tabs and scrollbars. Web designers build layouts around viewport width, which is why the same site can switch between desktop and mobile layouts when you narrow the window.
Common resolutions and what they are called
| Resolution | Name | Typical use |
|---|---|---|
| 1366 x 768 | HD (WXGA) | Budget laptops |
| 1920 x 1080 | Full HD, 1080p | Most monitors and laptops |
| 2560 x 1440 | QHD, 1440p | Gaming and office monitors |
| 3440 x 1440 | Ultrawide QHD | 21:9 gaming and productivity |
| 3840 x 2160 | 4K UHD | Large monitors, TVs, creative work |
If the physical pixel count is lower than what your monitor is rated for, the system is running below native resolution, which makes text soft. Set the recommended resolution in your display settings, then check sharpness with the text pattern in the monitor test.
Why your numbers might look wrong
- Scaling is on. A 1920 x 1080 laptop at 125 percent reports 1536 x 864. That is expected, not a fault.
- Browser zoom is not 100 percent. Press Ctrl and 0, or Command and 0 on a Mac, to reset zoom and see the true scaling.
- Several monitors. Values follow the monitor the window is on. Drag it across and they update.
- Privacy protections. Some browsers, such as Firefox with resist fingerprinting turned on, deliberately report rounded or fake screen values.
- Phones report layout sizes. An iPhone with a 1179 pixel wide panel reports about 393 CSS pixels at a pixel ratio of 3. Both numbers are correct, they just describe different things.
Where resolution matters most
Gaming
Games render at their own resolution, which should usually match your physical panel for the sharpest image. Higher resolutions cost frame rate, so pair this check with the FPS test and confirm your panel speed in the refresh rate test.
Design and development
Designers test layouts at common viewport widths, and developers need the pixel ratio to serve sharp images. The browser information tool adds browser, operating system and feature details to the same report.
Support and troubleshooting
Blurry text, tiny interfaces and cut-off windows are almost always resolution or scaling problems. Copying these values into a support request saves several rounds of back and forth.
Tips for the sharpest picture
- Always run each monitor at its native resolution and adjust size with scaling instead.
- Pick scaling steps that divide cleanly, such as 100, 150 or 200 percent, for crisper text on some systems.
- After connecting a new monitor, recheck, because systems sometimes pick a safe lower resolution first.
- Use a cable that supports your resolution and refresh rate together, especially for 4K at high refresh.
- Once the resolution is right, sweep the panel for faults with the dead pixel test.
Frequently asked questions
What is my screen resolution?
It is the first value on this page. For the number of real pixels on the panel, look at physical pixels, which accounts for your display scaling.
Why does my 4K screen show a lower resolution?
Your system is scaling the interface so text is readable. A 3840 x 2160 screen at 150 percent scaling reports 2560 x 1440 in CSS pixels, while still drawing every physical pixel.
What is device pixel ratio?
It is the number of physical pixels used for each layout pixel. A ratio of 2 means each CSS pixel is drawn with a 2 by 2 block of real pixels, which makes text and images sharper.
What is the difference between screen size and viewport?
Screen size is the whole display. The viewport is only the part of the browser window where the page is drawn, without toolbars, tabs or scrollbars.
Is this information sent anywhere?
No. Every value is read in your browser and shown only to you. Copy details puts the text on your own clipboard.
How do I change my screen resolution?
On Windows, open Settings, System, Display. On a Mac, open System Settings, Displays. Choose the recommended resolution for sharpest text.
What does 1080p mean?
It means 1920 by 1080 pixels, also called Full HD.
Why does my phone show a small resolution?
Phones report layout pixels, not physical pixels. Multiply by the device pixel ratio to get the real panel resolution.
Does zoom change the viewport?
Yes. Zooming in makes the viewport smaller in CSS pixels, which can switch sites to their mobile layout.
Related tools
Resolution checks out. Is the panel itself flawless?
Run through colour, uniformity, gradient and sharpness patterns to catch defects before your return window closes.