Screen Size Detector
Instantly detect your screen resolution, viewport size, orientation, pixel ratio, device type, and responsive CSS breakpoints in real time directly from your browser. No installation or registration required.
Live Screen Data
Updates automatically whenever your browser window is resized or your device orientation changes.
Screen Classification
View your current responsive CSS breakpoint based on your browser viewport size.
What Is a Screen Size Detector?
A Screen Size Detector is a free online tool that instantly displays your browser viewport size, screen resolution, device pixel ratio, screen orientation, device category, and responsive CSS breakpoint. It is useful for web developers, UI/UX designers, testers, students, and anyone building responsive websites.
Real-Time Detection
View your current browser width and height instantly. Information updates automatically whenever you resize the browser or rotate your device.
Responsive Breakpoints
Instantly identify whether your viewport falls into XS, SM, MD, LG, or XL responsive layouts.
Device Information
Detect whether you're browsing from a mobile phone, tablet, laptop, or desktop computer.
Pixel Ratio
View your device's pixel ratio for Retina displays and high-density screens used in modern devices.
How to Use the Screen Size Detector
The tool works automatically without requiring installation, registration, or browser extensions.
Step 1
Open the Screen Size Detector in any modern browser.
Step 2
Allow the page to load your current screen information automatically.
Step 3
Resize your browser window or rotate your device to watch the values update in real time.
Step 4
Use the displayed dimensions and responsive breakpoint while testing your website layout.
Information Displayed by the Tool
The Screen Size Detector provides several important measurements that help developers build responsive websites and applications.
Viewport Width
Displays the current browser width available for rendering web content.
Viewport Height
Shows the current browser height excluding browser interface elements.
Screen Orientation
Indicates whether your device is currently in portrait or landscape mode.
Device Type
Classifies your viewport as mobile, tablet, laptop, or desktop based on width.
Pixel Ratio
Displays the devicePixelRatio value used for high-density displays like Retina screens.
Responsive Breakpoint
Shows which CSS breakpoint category your current viewport belongs to for responsive design.
Common Responsive Breakpoints Explained
Responsive breakpoints are predefined screen widths used by CSS frameworks and developers to create layouts that adapt to different devices.
XS (Extra Small)
Usually used for very small smartphones with narrow screens.
SM (Small)
Commonly represents standard smartphones and larger mobile devices.
MD (Medium)
Typically covers tablets and smaller laptop screens.
LG (Large)
Suitable for desktop monitors and larger laptop displays.
XL (Extra Large)
Used for ultra-wide monitors, large desktop displays, and high-resolution screens.
Why Breakpoints Matter
Responsive breakpoints help ensure websites remain readable, accessible, and visually appealing on every screen size.
Common Screen Resolutions for Responsive Web Design
Understanding common screen resolutions and viewport sizes helps developers build responsive websites that look great across desktops, laptops, tablets, and smartphones. Testing your website on popular resolutions ensures a consistent user experience while using CSS media queries and responsive layouts.
1366 × 768
One of the most common laptop screen resolutions. It is widely used for testing responsive layouts on entry-level notebooks and business laptops.
1920 × 1080 (Full HD)
The most popular desktop and monitor resolution. Most websites are designed and optimized with Full HD displays in mind.
2560 × 1440 (QHD)
A common resolution for modern gaming monitors and professional displays that provides additional workspace while maintaining sharp image quality.
3840 × 2160 (4K UHD)
Used on high-resolution monitors and televisions. Developers should ensure websites scale properly on ultra-high-definition displays.
390 × 844 (Typical iPhone Viewport)
Represents the viewport size of many recent iPhone models in portrait mode. It is commonly used for mobile responsive testing.
412 × 915 (Typical Android Viewport)
A common Android viewport size found on many modern smartphones. Testing this viewport helps ensure layouts display correctly across Android devices.
Why Screen Resolutions Matter
Screen resolution determines the total number of pixels available on a display, while viewport size represents the area available for rendering web content inside the browser. Modern responsive websites rely on CSS media queries, flexible layouts, and responsive breakpoints to adapt content across different viewport sizes instead of targeting individual devices. Using a Screen Size Detector allows developers to verify viewport dimensions, pixel ratio, orientation, and responsive breakpoints during development and testing.
Frequently Asked Questions
Everything you need to know about the Screen Size Detector tool.
It shows your current screen width, height, orientation, pixel ratio, and device type in real time. It helps developers test responsive layouts easily.
No. Screen size refers to the viewport size (browser window), while resolution refers to physical pixels on the device screen.
Responsive websites adapt their layouts based on viewport width. Knowing your screen size helps developers test layouts across different devices.
Yes. The tool works on all devices including smartphones, tablets, laptops, and desktops.
Breakpoints are screen width ranges used in CSS to adjust layouts (XS, SM, MD, LG, XL) for different device sizes.
Explore Related Tools
Discover more free online developer and productivity tools.
Test Microphone
Test your microphone online and verify that your voice is being captured correctly.
Open Test Microphone →Test Keyboard
Check every key on your keyboard and identify keys that are not responding correctly.
Open Test Keyboard →Youtube Thumbnail Downloader
Download high-quality YouTube video thumbnails in multiple resolutions.
Open Youtube Thumbnail Downloader →Base64 Encoder & Decoder
Encode or decode Base64 strings instantly without installing software.
Open Base64 Tool →What is my IP Address
View your public IP address, approximate location, ISP, browser, and network information.
Open WhatsmyIP Address Tool →Image Converter
Convert images between PNG, JPG, WebP, BMP, GIF, and other popular formats.
Open Image Converter →