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Testpartout

Device tests · Display

Screen Resolution Test

This screen resolution test shows what your browser currently reports about your display: the screen size, the area left after taskbars and docks, the size of the page viewport, the device pixel ratio and the colour depth.

Browsers report most of these values in CSS pixels, a layout unit that is scaled by your operating system and zoom level. The numbers are useful for web layout, screenshots and troubleshooting, but they are not a guaranteed readout of your monitor's native panel resolution.

  • No permission needed
  • Live updates on resize
  • Browser-reported values

What does your browser report?

Read the screen size, available area, viewport, device pixel ratio and colour depth your browser exposes. No permission is needed and nothing is uploaded.

Values are in CSS pixels unless stated. They are browser-reported and are not guaranteed to match the monitor's native panel resolution.

Browser-reported display values

Not read yet
Screen size (CSS px)
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Available screen area (CSS px)
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Viewport (CSS px)
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Device pixel ratio
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Colour depth
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Pixel depth
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Screen size describes the display as the browser sees it; viewport is the page area inside the browser window. Device pixel ratio is a scaling ratio, not pixel density (PPI).

Your result

What your result means

Screen size and viewport size answer different questions. Screen size is how large the browser believes the whole display is; the viewport is only the part of the browser window where this page is drawn. Browser toolbars, tabs, window size and zoom all shrink or grow the viewport without changing the screen.

Device pixel ratio (DPR) tells you how many device pixels the browser uses for each CSS pixel in each direction. A DPR of 2 means content is drawn with twice the detail horizontally and vertically. DPR is a scaling ratio chosen by the operating system and browser — it is not pixels per inch and says nothing on its own about how sharp or large your monitor is.

  • Screen size (CSS px): the display dimensions as exposed to web pages, after operating-system scaling.
  • Available screen area: the screen minus areas the system reserves, such as a taskbar, dock or menu bar, when the browser reports it.
  • Viewport: the visible page area inside this browser window. It changes when you resize the window, zoom or enter fullscreen.
  • Device pixel ratio: device pixels per CSS pixel. It changes with display scaling settings and, in most desktop browsers, with page zoom.
  • Colour depth and pixel depth: the bits per pixel the browser reports for the display surface. Many browsers report 24 regardless of the panel's capability.
  • Orientation: shown only when the browser exposes the Screen Orientation API, for example landscape-primary at 0°.

Procedure

How the test works

  1. 01

    Read your screen

    Press “Read My Screen”. The page reads standard browser properties; no permission prompt appears.

  2. 02

    Compare screen and viewport

    Check how much smaller the viewport is than the screen. The difference is browser interface, window size and zoom.

  3. 03

    Resize or rotate

    Resize the window, change zoom or rotate a phone. The values update live after the first read.

  4. 04

    Try fullscreen

    Use the fullscreen button to see the viewport grow toward the full screen size without browser toolbars.

  5. 05

    Move between monitors

    On a multi-monitor setup, drag the window to another display and read again to see that display's values.

Methodology

How Testpartout measures this

The test reads standard web platform properties at the moment you press the button and again whenever the window size, fullscreen state or orientation changes.

What the implementation does

  • Screen size comes from screen.width and screen.height; available area from screen.availWidth and screen.availHeight.
  • Viewport size comes from window.innerWidth and window.innerHeight, which include the scrollbar area if one is shown.
  • Device pixel ratio comes from window.devicePixelRatio, shown with up to three decimal places because fractional scaling such as 1.25 or 1.5 is common.
  • Colour depth and pixel depth come from screen.colorDepth and screen.pixelDepth; orientation from screen.orientation when supported.
  • Values refresh on resize, orientationchange and fullscreenchange events. No values are estimated, rounded to marketing resolutions or converted into PPI.

Limits of a browser measurement

  • CSS pixels are not guaranteed physical pixels. Multiplying screen size by DPR often approximates device pixels, but operating-system scaling, browser zoom and privacy protections can make that differ from the native panel resolution, so this page does not present it as a measurement.
  • Some browsers deliberately round or standardise reported values to reduce fingerprinting.
  • On multiple monitors, values describe the display the browser window is currently on, and some browsers only update after a window move or reload.
  • The test cannot measure physical size, pixel density, panel type, HDR capability or refresh rate.
  • Colour depth reported to web pages is frequently fixed at 24-bit and should not be read as proof of a panel's bit depth.

Privacy

What happens to your data

This section describes the behaviour of the code on this page, not an intention.

  • No camera, microphone, location or other permission is requested.
  • Display values are shown only on this page and are not saved, uploaded or sent to analytics.
  • Only consent-controlled start and complete events, with no measurement values, may be recorded.

Troubleshooting

If the test does not behave as expected

The resolution is lower than my monitor's box

Your operating system is probably scaling the display (for example 150%). Web pages see the scaled size in CSS pixels. Check the display settings for the native resolution and scaling percentage.

DPR changed when I zoomed

Most desktop browsers change devicePixelRatio with page zoom. Reset zoom (Ctrl/Cmd + 0) to see the value that comes from system scaling.

Values did not change on my second monitor

Move the browser window fully onto the other display, then press Read again. Some browsers report the primary display until the window is moved.

Fullscreen did not open

Fullscreen must be allowed by the browser and may be blocked in embedded frames or some mobile browsers. Use the browser's own fullscreen command instead.

The viewport is a bit narrower than expected

A visible vertical scrollbar is included in some measurements and not others. Classic scrollbars typically take a small strip of the window.

Factors

Why reported values differ from the spec sheet

Several layers sit between the physical panel and what a web page can see. Each one can change the numbers.

Operating-system scaling

Scaling such as 125%, 150% or 200% enlarges text and interface. The browser then reports a smaller CSS screen size with a higher DPR.

Browser zoom

Page zoom changes the viewport in CSS pixels and usually DPR, while the screen size normally stays the same.

Browser interface

Tabs, address bar, bookmarks and side panels take space from the viewport. Fullscreen removes most of them.

Taskbars and docks

Reserved system areas reduce the available screen area but not the total screen size.

Multiple monitors

Each display can have its own resolution and scaling. Values follow the display the window is on, which can surprise users with mixed setups.

Mobile browsers

Phones usually report a CSS width of a few hundred pixels with a DPR of 2–3, even though the panel has many more physical pixels.

Privacy protections

Some browsers round or spoof screen values to make devices harder to fingerprint.

FAQ

Frequently asked questions

What is my screen resolution?
Press Read My Screen to see the screen size your browser reports in CSS pixels, plus the device pixel ratio. For the native panel resolution, check your operating system's display settings or the manufacturer's specification; the browser value can be scaled.
Why is the browser resolution different from my monitor's box or spec?
The box lists the panel's native pixels. Browsers report CSS pixels after operating-system scaling, so a 3840 × 2160 panel at 150% scaling typically appears as 2560 × 1440 with a DPR of 1.5.
What is DPR (device pixel ratio)?
It is the number of device pixels the browser uses per CSS pixel in each direction. It reflects scaling and zoom, not pixels per inch, so it cannot tell you physical sharpness or screen size on its own.
Why does browser zoom change the viewport but not the screen size?
Zoom changes how large CSS pixels are drawn inside the page, so fewer of them fit in the window. The screen size describes the whole display and is usually unaffected by page zoom.
Why do multiple monitors report different values?
Each monitor can have its own resolution and scaling. The browser reports values for the display the window is on, and some browsers only update after you move the window or reload.
What is the difference between screen size and viewport size?
Screen size is the whole display as seen by the browser. Viewport size is just the page area inside the browser window, which shrinks with toolbars, window size and zoom.
Does this test measure PPI or physical size?
No. Web pages cannot reliably read physical dimensions or pixel density, so this page does not estimate PPI.
Is any of this information uploaded?
No. The values stay on this page. Analytics, if you consent, only records that the test started and completed, without any display values.

Found an issue with this test? Report it.