Screen Resolution Checker – Find Your Display Size & DPI
Check your screen resolution and viewport size.
How to use this screen resolution checker
- Open this page and your screen resolution, viewport size, available size, and device pixel ratio display automatically
- Resize your browser window to see the Viewport Size value update live
- Compare Screen Resolution against Available Size to see how much space system UI like a taskbar or dock takes up
- Check the Device Pixel Ratio value to see whether you are on a standard or high-DPI (Retina-style) display
- Reload the page after changing display scaling settings or connecting an external monitor to see updated values
- Note the Screen Resolution value when reporting a display-related bug or comparing device specifications
Frequently Asked Questions
What is screen resolution?
Screen resolution is the number of pixels displayed on your screen. It's measured as width × height (e.g., 1920 × 1080).
What is the difference between screen and viewport?
Screen resolution is your physical display size. Viewport is the visible area of the browser window, which may be smaller if the window is resized or zoomed.
What is device pixel ratio?
Device pixel ratio is the ratio between physical pixels and CSS pixels. High-DPI displays (like Retina) have ratios greater than 1, meaning more physical pixels per CSS pixel.
A screen resolution checker shows you the exact pixel dimensions of your display, browser viewport, and available screen space, along with your device's pixel ratio. This is essential for web developers and designers testing responsive layouts and breakpoints, QA testers documenting the exact screen a bug was seen on, people troubleshooting display or scaling issues, and anyone buying a monitor or comparing devices who wants to confirm the resolution actually being reported by the operating system. Because screen resolution, browser viewport, and usable screen space are three different measurements that are often confused, seeing them side by side makes it easy to understand exactly how much space is available at each level.
What is screen resolution?
This tool reads screen.width and screen.height for your full physical display resolution, window.innerWidth and window.innerHeight for the current browser viewport size, screen.availWidth and screen.availHeight for the screen space left after taskbars, docks, or other system UI are excluded, and window.devicePixelRatio for the ratio between physical device pixels and CSS pixels. It listens for the browser's resize event so the viewport values update live if you resize the window. High-DPI displays such as Retina screens report a device pixel ratio greater than 1, meaning each CSS pixel is rendered using multiple physical pixels for sharper images and text. All of these values are standard browser properties read directly via JavaScript, with nothing sent anywhere.
Common use cases
- Responsive web design testing: Checking exact viewport dimensions while verifying CSS breakpoints and media queries
- Bug reports and QA: Recording the precise screen resolution and pixel ratio a rendering issue occurred on
- Display troubleshooting: Confirming that an operating system is reporting the expected resolution after a scaling or driver change
- Device comparisons: Checking the actual resolution and pixel ratio reported by a new monitor, laptop, or phone
- Multi-monitor setups: Verifying which resolution values are reported when a browser window is on a secondary display
- High-DPI asset planning: Checking a device's pixel ratio to decide whether to serve standard or retina-quality images
Limitations and common mistakes
- Screen Resolution reflects the operating system's reported display size, which can be affected by OS-level display scaling and may not match the monitor's native panel resolution
- Viewport Size only measures the current browser window, not the full screen, so it will differ from Screen Resolution whenever the browser is not maximized
- Available Size depends on OS chrome like taskbars, docks, or notches, and can vary between operating systems even at the same screen resolution
- Device Pixel Ratio can change if the user zooms the browser or adjusts OS display scaling, so the value reflects the current state, not a fixed hardware constant
- On multi-monitor setups, values reflect whichever display currently contains the browser window and will change if the window is moved to a different monitor