Last updated: March 2026
What Is Screen Resolution?
Screen resolution refers to the number of pixels your display can show, expressed as width times height. A 1920x1080 display has 1,920 horizontal pixels and 1,080 vertical pixels, totaling over 2 million individual pixels rendering your content.
Higher resolution means more pixels, which translates to sharper text, more detailed images, and more screen real estate. A 4K display (3840x2160) has four times the pixels of a 1080p display, which is why text looks noticeably crisper at the same physical screen size.
1920x1080 remains the most common desktop resolution at roughly 23% market share worldwide, followed by 2560x1440 and 1366x768. On mobile, fragmentation is much higher — there are hundreds of unique screen resolutions across Android devices alone.
How to Use This Screen Size Checker
Step 1: Open this page in any browser. Your screen resolution, browser window size, viewport, and device pixel ratio are detected instantly.
Step 2: Resize your browser window by dragging a corner or edge. Watch all values update in real time — changed values flash green.
Step 3: Check the responsive breakpoint indicator to see which CSS and Tailwind breakpoints your current viewport falls into.
Step 4: Review the device match to see which common device your screen resolution most closely matches.
Step 5: Use Ctrl/Cmd + +/- to zoom your browser and observe how DPR and viewport values change accordingly.
Key Features
Live updates on resize. Every value updates instantly as you resize your browser window, rotate your device, or change zoom level. Green flash animation highlights changed values.
Comprehensive measurements. Screen resolution, browser window, viewport, DPR, effective resolution, orientation, and color depth — all in one place.
Responsive breakpoint detection. Instantly see which CSS/Bootstrap and Tailwind breakpoints your viewport falls into, essential for responsive web development.
Device matching. Compares your effective resolution against 25+ common devices to identify the closest match.
System info. Detects your browser, operating system, and touch support without any plugins or extensions.
Privacy first. Everything runs client-side in your browser. No data is collected or transmitted.
Understanding Device Pixel Ratio
Device Pixel Ratio (DPR) is the ratio between physical pixels and CSS pixels on your display. A standard monitor has a DPR of 1, meaning one CSS pixel equals one physical pixel. Modern high-DPI displays often have a DPR of 2 or 3.
When Apple introduced Retina displays, they doubled the pixel density. A MacBook with a reported resolution of 1440x900 actually has 2880x1800 physical pixels (DPR = 2). This makes text and UI elements appear at a comfortable size while rendering with twice the detail.
For web developers, DPR matters because images need to be served at 2x or 3x resolution to look sharp on high-DPI screens. A 100x100 CSS pixel image needs to be 200x200 or 300x300 actual pixels. This is why responsive images with srcset are essential for modern web development.
Mobile accounts for roughly 59% of global web traffic, and most smartphones have a DPR of 2-3. Designing for DPR 1 alone means your site may look blurry for the majority of visitors.
CSS Breakpoints for Responsive Design
Responsive design uses CSS media queries with breakpoints to adapt layouts for different screen sizes. The most common breakpoint systems come from Bootstrap (576/768/992/1200/1400px) and Tailwind CSS (640/768/1024/1280/1536px).
When building responsive sites, design mobile-first — write your base CSS for the smallest screen, then add breakpoints to enhance the layout for larger screens. This approach ensures your site works well on all devices and results in cleaner, more maintainable CSS.
This tool shows which breakpoint your current viewport falls into for both Bootstrap and Tailwind systems, making it easy to test responsive layouts by simply resizing your browser window.
Frequently Asked Questions
What is the difference between screen resolution and viewport size?
Screen resolution is the total number of pixels your monitor can display (e.g., 1920x1080). Viewport size is the area inside your browser window where web content renders, minus toolbars, scrollbars, and browser chrome. The viewport is always smaller than or equal to the screen resolution.
What is Device Pixel Ratio (DPR)?
Device Pixel Ratio is the ratio of physical pixels to CSS pixels on your display. A DPR of 2 (common on Retina/HiDPI displays) means each CSS pixel is rendered using a 2x2 grid of 4 physical pixels, resulting in sharper text and images. Standard monitors have a DPR of 1.
How do I check my screen resolution?
This tool shows your screen resolution instantly. It reads window.screen.width and window.screen.height, which report the resolution of your monitor in CSS pixels. Multiply by your Device Pixel Ratio to get the physical pixel count (effective resolution).
What are CSS breakpoints and why do they matter?
CSS breakpoints are viewport widths where a website's layout changes to accommodate different screen sizes. Common breakpoints include 768px (tablet), 1024px (desktop), and 1280px (large desktop). Developers use these to build responsive designs that work on all devices.
What is a Retina display?
A Retina display is Apple's marketing term for screens with a Device Pixel Ratio of 2 or higher. These displays pack more physical pixels into each CSS pixel, making text and images appear sharper. Most modern smartphones, tablets, and laptops have HiDPI screens with DPR of 2 or 3.
Why does my screen resolution look different from my display's spec sheet?
Operating systems often use display scaling (e.g., 150% or 200% on Windows, or default Retina scaling on macOS) to make UI elements a comfortable size. This means the reported CSS resolution may be lower than the physical pixel count. Multiply by the DPR to get the actual physical resolution.