Screen Resolution Test — Free Online Test
Our Resolution Test reports your monitor's current resolution, device pixel ratio, and physical DPI so you can confirm the OS is driving the display at its native panel resolution. Running at non-native resolution causes soft text and blurry UI.
How to use the Screen Resolution Test
- Load the page and read the reported resolution.
- Compare it against the panel's advertised native resolution.
- If they differ, change the display resolution in your OS settings.
How to interpret your results
Matching values mean you are running native. Lower reported resolution means the OS is scaling; text will look soft. Higher DPI (Retina) devices report a device-pixel-ratio above 1.
Common issues and what they mean
Windows locked to a low resolution
Install the correct GPU driver. Basic Microsoft display driver caps many panels at 1024x768.
Text tiny at native 4K
Increase scaling in Display settings to 150% or 175%.
When to run this test
- After a fresh OS install.
- When connecting a new external monitor.
Native resolution, logical pixels and why the numbers differ
Every fixed-pixel display has exactly one native resolution — the literal count of physical subpixel triads on the panel. Feed it anything else and a scaler, either in the monitor or in the GPU, has to interpolate. Interpolation invents pixel values that were never in the source, and the result is the soft, slightly doubled look that most people describe as "blurry" without being able to say why.
What a browser reports is not the physical count but the logical, or CSS, resolution: physical pixels divided by the device pixel ratio. A 4K laptop at 200% scaling honestly reports 1920 by 1080 CSS pixels with a device pixel ratio of 2. Multiply the two together and you recover the real panel resolution, which is exactly what this tool does for you.
This distinction matters for anyone building or testing websites. Media queries, viewport units and breakpoints all operate in CSS pixels, so a design that looks correct on a 1440p desktop can behave like a small tablet layout on a high-DPI laptop reporting far fewer logical pixels.
When the reported resolution is wrong
The most common cause is a cable or port limitation rather than the display itself. HDMI 1.4 tops out at 4K/30 Hz, so a monitor forced through an old cable may only offer 4K at an unusable refresh rate or drop to 1440p entirely. DisplayPort 1.2 handles 4K/60 comfortably; USB-C alt mode depends on how many lanes the hub reserves for video, which is why a docking station frequently costs you either resolution or refresh rate.
Driver state is the second cause. After a clean Windows install or a failed driver update, the generic Microsoft Basic Display Adapter exposes only a handful of low modes. Installing the correct Intel, AMD or NVIDIA driver restores the full EDID-derived list. On Linux, a monitor with a broken EDID may need an explicit modeline or the video kernel parameter.
Finally, check the monitor's own menu. Many panels ship with a bandwidth-saving mode — labelled DisplayPort 1.1 compatibility, HDMI Ultra HD Deep Colour, or similar — turned off by default, and enabling it is the only way to unlock the full resolution and refresh combination the panel supports.
Frequently asked questions
Why does my 4K monitor only report 1920x1080?
Windows may be scaling for display; the reported CSS resolution reflects logical pixels, not physical.
Is running below native resolution ever a good idea?
Only for older games where framerate matters more than clarity, and even then prefer an exact half of native so each logical pixel maps to a clean block of four.
Why did my resolution options disappear after a Windows update?
The update most likely replaced your GPU driver with the generic Microsoft display adapter. Reinstalling the vendor driver restores the full mode list.