What Is My Screen Resolution?
Resolution, Pixel Density, Refresh Rate & Dead Pixel Test
Use our free screen resolution checker to instantly detect your display resolution in pixels, viewport size, device pixel ratio (DPR), color depth bits, screen aspect ratio, and refresh rate (Hz). This online screen size tool also checks CSS pixels vs physical pixels, screen orientation, available screen width and height, PPI density, and Retina display status. Includes a fullscreen dead pixel test with color cycling. The best monitor resolution tester and monitor specs checker — check screen DPI online free with no software needed. A professional screen size pixels finder for designers, developers, and gamers.
Quick Answer: What Is Your Screen Resolution?
Your screen resolution is the number of pixels your monitor displays (width × height). Our screen resolution checker detects this instantly along with DPR, color depth, aspect ratio, refresh rate, viewport dimensions, and PPI. It also includes a fullscreen dead pixel test for monitor hardware detection.
Your Screen Resolution
Detecting...
Resolution & Size
Display Quality
Browser & Device
Robert Harrison
OSINT & Network Utility Expert
Robert specializes in display technology, hardware analysis, web development tools, and network diagnostics. He helps developers and designers understand screen specifications for building responsive, pixel-perfect interfaces.
View All ArticlesWhat Is a Screen Resolution Checker and What Does It Detect?
Worth knowing before you read the numbers below: everything on this page is also visible to every site you visit. Screen resolution, colour depth, device pixel ratio and orientation are read straight from the browser with no permission prompt, and together they are one of the strongest components of a browser fingerprint. An unusual resolution narrows you down fast — 1920×1080 hides you in a crowd, 3440×1440 does not. This is exactly why Tor Browser letterboxes its window to rounded dimensions instead of letting you maximise it, a trade-off we cover in Tor Browser versus a VPN. The same panel also measures the canvas, audio and font signals that get combined with it, and our write-up on how fingerprinting follows you after you clear cookies explains why deleting them changes nothing here.
A screen resolution checker reads your monitor's display resolution (W × H) in pixels — the total number of horizontal and vertical dots your screen can show. Our online screen size tool goes far beyond basic resolution: it detects viewport size, device pixel ratio (DPR), color depth bits, screen orientation, aspect ratio, refresh rate (Hz), available screen width and height, PPI density, CSS pixels vs physical pixels, and Retina display status.
This data is essential for web developers building responsive layouts, designers who need to serve correctly-sized images for different DPR values, gamers verifying their monitor specs, and anyone checking a new display for defects. Our monitor resolution tester works directly in your browser — no software downloads required.
15+ Data Points: Our screen resolution checker detects screen resolution, physical pixels, available screen area, browser window, viewport dimensions, aspect ratio, DPR, color depth, refresh rate, PPI, Retina check, orientation, touch, dark mode, and hardware acceleration — all from your browser screen resolution check.
How to Check My Screen Resolution in Pixels Online
Open this page on any device — desktop, laptop, phone, or tablet — and your screen resolution appears instantly. Our screen size pixels finder uses JavaScript's screen.width and screen.height APIs to read your native display resolution. The value shown is your monitor's actual pixel count, not the scaled resolution your OS might display.
// How we detect your resolution
Screen Resolution: screen.width × screen.height
Physical Pixels: (screen.width × DPR) × (screen.height × DPR)
Viewport Size: window.innerWidth × window.innerHeight
Available Screen: screen.availWidth × screen.availHeight
// Example: 1920×1080 at 1.5x DPR
CSS Pixels: 1920 × 1080
Physical Pixels: 2880 × 1620 (actual hardware dots)
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CSS Pixels vs Physical Pixels: Understanding DPR for Designers
One of the most confusing concepts in display technology is the difference between CSS pixels and physical pixels. On a standard 96 DPI monitor, 1 CSS pixel = 1 physical pixel. But on a Retina display with 2x device pixel ratio, 1 CSS pixel = 4 physical pixels (2×2 grid). This is why images look sharper on HiDPI screens.
| Display Type | CSS Resolution | DPR | Physical Pixels |
|---|---|---|---|
| Standard 1080p | 1920×1080 | 1x | 1920×1080 |
| MacBook Retina | 1440×900 | 2x | 2880×1800 |
| iPhone 15 | 390×844 | 3x | 1170×2532 |
| 4K Monitor (150%) | 2560×1440 | 1.5x | 3840×2160 |
For Designers: Always serve images at 2x your CSS size for Retina displays. If an image is 300×200 CSS pixels, the source file should be 600×400. Our screen DPI and PPI checker for designers shows your exact DPR to get this right.
How to Check Screen DPI: Pixel Density Explained
Pixel density is the one number on this page a browser genuinely cannot work out on its own, and it is worth being straight about why. PPI — pixels per inch — needs two things: the pixel count, which the browser has, and the physical size of the panel in inches, which it does not. There is no API for inches. Nothing a web page can call will tell it whether those 3840 pixels are spread across a 27-inch monitor or a 15-inch laptop, and those two answers differ by nearly a hundred PPI.
Most tools paper over this by multiplying 96 by your device pixel ratio and calling the result an estimate. That returns 96, 192 or 288 and nothing in between, so it is wrong for almost every desktop monitor ever made. We used to do the same thing. Now the panel above simply asks: type your screen diagonal into the box and the density is calculated from your actual pixel grid.
# The arithmetic, if you want to check it yourself
PPI = √(width² + height²) ÷ diagonal inches
# A 27-inch 4K panel
√(3840² + 2160²) ÷ 27 = 163 PPI
# The same panel, guessed from device pixel ratio
96 × 1 = 96 PPI // out by 40 per cent
Use the pixel count the tool already shows you, and measure the diagonal corner to corner across the glass — not the bezel, and not the number on the box, which is often rounded. A tape measure is fine. Get that right and the figure is exact.
PPI (Pixels Per Inch) measures how tightly packed the pixels are on your display. Higher PPI means sharper text and images. To check screen DPI online, type your screen diagonal into the panel above — the density is then exact, because it is worked out from your real pixel count rather than guessed from your pixel ratio.
- ~96 PPI: Standard desktop monitors (24" at 1080p). Text is readable but individual pixels are visible up close.
- ~120-220 PPI: Laptop displays and high-end monitors. Text looks smooth and clean.
- ~300+ PPI: Smartphones and tablets. At normal viewing distance, pixels are invisible — this is the "Retina" threshold.
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Aspect Ratio Detection: 16:9, 16:10, 21:9 and More
Your screen aspect ratio defines the shape of your display. Our tool calculates it automatically from your width and height. The most common ratios are 16:9 (standard widescreen), 16:10 (productivity laptops like MacBook), 21:9 (ultrawide monitors), and 4:3 (legacy displays).
Knowing your aspect ratio matters for responsive design, video production (matching content to display shape), and gaming (ultrawide gives wider field of view). Our display resolution finder shows the exact calculated ratio. Check headers with our Headers Analyzer. Test DNS with our DNS Lookup.
Refresh Rate Detection: How to Find Your Monitor's Hz in Browser
Our tool measures your refresh rate (Hz) using requestAnimationFrame timing — counting how many frames your browser renders per second. Standard monitors run at 60Hz, gaming monitors at 144Hz or 240Hz, and many phones at 90Hz or 120Hz.
Treat the number as a floor, not a verdict. The browser is reporting how fast it managed to draw, which is not quite the same as what the panel is capable of. A 144Hz monitor will read 60Hz if the browser is throttling, if the tab is in the background, if a laptop is on battery saver, or if something else on the machine is loading the GPU. Put the window in the foreground, plug the laptop in, close what you can and re-run it. If it still reads low, the authoritative answer is in the monitor's own on-screen menu or in your OS display settings — not in any browser.
// How we measure refresh rate
let frames = 0, start = performance.now();
function count(ts) {
frames++;
if (ts - start >= 1000) {
// frames = your Hz (60, 120, 144, etc.)
return;
}
requestAnimationFrame(count);
}
Note: Browser-measured Hz may differ slightly from your monitor's native rate due to V-Sync, power saving, or background throttling. For most accurate results, keep this tab in the foreground. Verify domain with WHOIS.
Dead Pixel Test: How to Check Your Monitor for Defects
Our fullscreen dead pixel test fills your entire screen with solid colors — red, green, blue, white, and black — one at a time. Click to cycle through colors. This is the standard method professionals use to detect panel defects before accepting a new monitor.
- Dead Pixels: Appear as black dots on white or bright backgrounds. The transistor has failed permanently. Most manufacturers replace panels with 3+ dead pixels under warranty.
- Stuck Pixels: Appear as a single colored dot (red, green, or blue) on black background. Sometimes fixable by rapidly cycling colors to "unstick" the sub-pixel.
- Backlight Bleed: On the pure black test, look for light leaking from edges or corners. Common in LED/IPS panels. Excessive bleed is a warranty defect.
Best Practice: Run the test in a dark room for maximum visibility. Click to advance through R → G → B → White → Black. Press ESC or complete the cycle to exit. Check email with our Email Verifier.
Viewport Size vs Screen Resolution: What Web Developers Need
If you are testing what a site can infer about a visitor rather than how a layout reflows, resolution is only one input. The timezone consistency check catches the mismatch that gives away a proxy — an IP in one country reporting a browser clock set to another — and the full browser info readout lists every header and property being handed over alongside the display data.
Your viewport size (the actual rendering area in the browser) is different from your screen resolution. The viewport excludes the browser toolbar, address bar, and OS taskbar. Understanding this difference is critical for building responsive web applications.
Our tool shows three key measurements: Screen Resolution (full display), Available Screen (minus taskbar), and Browser Viewport (minus browser chrome). CSS media queries use the viewport, not the screen resolution. This is why a "1920px" breakpoint might not trigger even on a 1920px screen with a sidebar open.
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Common Screen Resolutions: A Standards Guide
| Name | Pixels | Ratio | Use Case |
|---|---|---|---|
| HD (720p) | 1280×720 | 16:9 | Budget laptops, tablets |
| Full HD (1080p) | 1920×1080 | 16:9 | Standard monitors, gaming |
| QHD (1440p) | 2560×1440 | 16:9 | High-end gaming, productivity |
| 4K UHD | 3840×2160 | 16:9 | Photo/video editing, cinema |
| Ultrawide | 3440×1440 | 21:9 | Multitasking, immersive gaming |
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Complete Screen Diagnostic Workflow
- Step 1: Open our screen resolution checker to see your resolution, DPR, and aspect ratio.
- Step 2: Check CSS vs physical pixels — essential for responsive design decisions.
- Step 3: Review refresh rate — verify your gaming monitor is running at expected Hz.
- Step 4: Run the dead pixel test — cycle through R/G/B/W/K in a dark room.
- Step 5: Check PPI — verify Retina display status for image asset planning.
- Step 6: Copy all results for documentation or QA reports.
- Step 7: Run our Hardware Info for GPU and CPU specs.
- Step 8: Finish with what the display says about you rather than to you. The browser info readout lists every property being handed to sites alongside your resolution, and the full leak test scores how identifying the combination is. If your resolution is an unusual one, that is the page that will tell you how much it narrows you down.
Frequently Asked Questions About Screen Resolution
Q What is a screen resolution checker?
A screen resolution checker detects your display resolution in pixels, viewport size, DPR, color depth, aspect ratio, refresh rate, and more. Our monitor specs checker reads 15+ data points from your browser.
Q How to check phone screen resolution online?
Open our screen resolution test on your phone. It detects resolution, viewport, DPR, color depth, and orientation instantly. Works on iPhone, Android, iPad — no app needed.
Q What is CSS pixels vs physical pixels?
CSS pixels are logical layout units. Physical pixels are actual hardware dots. On 2x DPR Retina displays, 1 CSS pixel = 4 physical pixels. Our tool shows both so you see effective pixels vs actual resolution.
Q How to find refresh rate in browser free?
Our tool measures refresh rate (Hz) using requestAnimationFrame — counting rendered frames per second. Detects 60Hz, 120Hz, 144Hz, 240Hz monitors directly in browser.
Q What is device pixel ratio?
Device pixel ratio (DPR) is the ratio of physical pixels to CSS pixels. DPR 2x = Retina display. Designers need this to serve correctly-sized images. Our check screen DPI online tool shows your exact DPR.
Q How to test for dead pixels?
Click "Dead Pixel Test" to fill your screen with solid colors (R/G/B/W/Black). Dead pixels = black dots on bright backgrounds. Stuck pixels = colored dots on black. Darken your room for best results.
Q How to check screen DPI online?
Enter your screen diagonal in the panel above and the density is worked out from your real pixel grid — √(w²+h²) ÷ inches. No browser can read the physical size of a panel on its own, so a tool that reports PPI without asking is multiplying 96 by your pixel ratio and calling it an estimate. For reference: desktop monitors land around 80–110 PPI, laptops 120–260, phones 400–500.
Q How to find aspect ratio without software?
Our tool auto-calculates aspect ratio from your screen dimensions. Common: 16:9 (widescreen), 16:10 (MacBook), 21:9 (ultrawide), 4:3 (legacy). No software — browser screen resolution check only.
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Free Monitor Test — No Software Required
Our screen resolution checker detects resolution, DPR, aspect ratio, refresh rate, color depth, and includes a dead pixel test. Everything your display reports, on one page.