Resolution → aspect, class name, PPI, raw size (image + video)

Screen resolution as a device fingerprinting signal

Screen resolution is one of the primary signals used in browser fingerprinting. The combination of screen.width, screen.height, and device pixel ratio, joined with User-Agent, OS, and timezone, can identify a specific device within a large population with high accuracy. Unusual resolutions — DCI 4K at 4096×2160, non-standard HiDPI configurations, or ultra-wide variants — have especially high discriminative power.

Online resolution tools sometimes auto-collect the visiting browser’s resolution and report it to analytics alongside other device characteristics. Accessing a tool to ‘check my resolution’ can itself be a fingerprinting event. This tool does only the arithmetic you request and collects nothing.

What online resolution calculators sometimes collect

Many resolution and aspect-ratio calculators run advertising models that inject multiple analytics scripts. Some capture screen.width, screen.height, devicePixelRatio, and viewport size automatically on page load and send them to third-party measurement endpoints before the user has typed anything. The act of visiting the page to look up a resolution becomes a data-sharing event.

This tool performs only the calculations you explicitly request. Entered resolution values stay in page memory and are never transmitted. The reference dictionary of 25 standard resolutions is bundled statically.

Pure browser arithmetic for GCD, PPI, memory, and bandwidth

Aspect ratio reduction uses the Euclidean GCD algorithm. Nearest-standard matching ranks entries within 5% aspect tolerance by log2 distance. Megapixel count, uncompressed RGB/RGBA memory footprint (pixels × 3 or 4 bytes), and 60-fps raw bandwidth (pixels × 3 bytes × 8 bits × 60) are integer or floating-point multiplications. PPI is the Pythagorean diagonal in pixels divided by the entered diagonal in inches. All computations run entirely in browser JavaScript with no external API calls.

The 25 standard-resolution dictionary is compiled into the bundle at build time. Entering a production spec, an unreleased device target, or an internal broadcast resolution yields results without any of those numbers leaving the device.

Pre-production checks for video encoding, design, and display

Before selecting an encoder profile for a 4K video project, check the raw uncompressed bandwidth to confirm the pipeline can handle it. Before creating a design mockup artboard, verify that your intended resolution maps to a named standard and confirm the aspect ratio is what the platform expects. Before shipping a HiDPI asset, calculate the PPI at the target screen size to verify Retina threshold (roughly 200 PPI at typical viewing distance). These checks take seconds locally and avoid the slower feedback loop of discovering issues in production.

Euclidean GCD, PPI calculation, and raw bandwidth formulas

Aspect ratio reduction uses the Euclidean algorithm: while (b) { [a, b] = [b, a % b]; } return a; — O(log min(a, b)) and one line in JavaScript. Dividing both dimensions by the GCD gives the smallest integer ratio: 1920×1080 reduces to 16:9 via GCD 120. One caveat is that some marketed resolutions round oddly: 1366×768 reduces to 683:384 via GCD 2 even though it is colloquially “16:9”, because 1366 is a rounded-up approximation of 1365.33. The tool’s standard-name matcher therefore uses a ±5% aspect tolerance and picks the closest reference entry by log2 distance, so common near-16:9 resolutions still surface a recognisable name.

PPI (pixels per inch) is the diagonal pixel count divided by the diagonal in inches: diagonalPixels = sqrt(w^2 + h^2); PPI = diagonalPixels / diagonalInches. iPhone 15 Pro at 2556×1179 on a 6.1-inch diagonal works out to roughly 461 PPI. Apple’s “Retina threshold” depends on viewing distance: about 326 PPI for a phone held at 12 inches, 220 PPI for a Mac at 20 inches, 60 PPI for a TV at 80 inches — the angular pixel density at which individual pixels become indistinguishable. The raw 60-fps RGB video bandwidth is width × height × 3 bytes × 8 bits × 60 = width × height × 1440 bps. 4K UHD comes to roughly 12 Gbps, comfortable on HDMI 2.1 (48 Gbps) but requiring 4:2:0 chroma subsampling on HDMI 2.0 (18 Gbps).

Resolution naming history and the inconsistencies it produced

“4K” refers to two distinct standards: cinema DCI 4K (4096×2160, SMPTE 2048-2) at a 1.90 aspect ratio, and consumer 4K UHD (3840×2160, ITU-R BT.2020) at 1.78. The roughly 6 % aspect mismatch means pillarbox or letterbox bars when one is shown on the other. The “8K” name has the same split: DCI 8K (8192×4320) versus UHD-2 (7680×4320). On phones, the suffix + (FHD+, QHD+) indicates a taller-than-16:9 aspect (19.5:9 or 20:9) but is not industry-standard — Samsung’s FHD+ is 2280×1080, Google Pixel’s FHD+ is 2400×1080, so the label alone is not enough.

The CRT-era VGA/SVGA/XGA/SXGA/UXGA/QXGA family, the wide-screen W-prefixed family (WXGA, WSXGA+, WUXGA, WQHD), and the TV-derived HD/FHD/QHD/UHD family all coexist, so the same resolution often has multiple names — 2560×1440 is WQHD, QHD, and 1440p simultaneously. The 25 entries bundled in this tool cover the main video standards plus mobile-first formats (TikTok 1080×1920, Instagram 1080×1080, iPhone tall aspects, iPad, Apple Watch). Another common source of confusion is the gap between physical pixel resolution and CSS logical resolution: a Retina Mac may report screen.width as 1440 while the panel is 2880 pixels wide, because devicePixelRatio is 2. Calculations that mix the two yield results that look “off by 2x”. When the input is an actual image file rather than a numeric resolution, image-aspect-find inspects each file’s intrinsic width / height, and screen-size-calc helps work backward from a target physical diagonal so the PPI numbers above land on the right reference distance.