Screen Resolution

Introduction

The DeviceHub Screen Resolution tool is a free online readout of screen, window, and viewport dimensions plus devicePixelRatio so you can see what the web platform believes about layout geometry, without EDID utilities, GPU control panels, or manufacturer spec sheets. Designers validating responsive breakpoints, front-end engineers chasing overflow on real laptops, support staff collecting sizes from remote users, QA comparing Retina scaling with office 1080p panels, and shoppers confirming a tablet CSS viewport all get an instant snapshot that needs no permission prompt because geometry APIs are not microphone or camera flows. Open the page on the display under test, keep browser zoom at 100%, and separate three ideas marketing blurbs combine: screen metrics the browser exposes, outer window size including chrome, and the layout viewport your CSS actually uses. DeviceHub is honest: these numbers are CSS-pixel oriented web readouts, not a warranty certificate of the panel native HDMI mode, and OS scaling plus browser toolbars routinely make a 1920×1080 monitor read differently inside a windowed tab. Pair with Device Information in the separate Hardware category when tickets need broader hardware capability context beyond pure layout sizes. Pair with Browser Information for engine identity, Display Aspect Ratio Test when shape labeling matters, and User Agent only when the dispute is software identity rather than pixels. Print designers converting CSS pixels to physical print units misunderstand this page, it reports layout viewport math for screen media, not PDF point sizes. Ultrawide owners validating 3440×1440 desktop scaling see how Windows 125% scaling shrinks reported CSS widths versus box labels on the monitor carton. Kiosk vendors validating portrait-mode totems compare innerHeight before and after hiding the Android navigation bar. Trade-show demo laptops often run 125% scaling while external monitors stay at 100%, moving the browser window between them changes every reported field without any “bug” in DeviceHub math. Projector overscan cropping affects perceived layout viewport on cheap HDMI projectors, geometry readout still reflects browser belief, not bezel crop. Ultrawide monitors with fractional Windows scaling report CSS widths that confuse designers expecting literal 3440 marketing pixels, paste DPR beside width in layout tickets.

What this tool does

The page surfaces width and height for screen-oriented metrics, window inner and outer dimensions when exposed, layout viewport sizes, devicePixelRatio, and live updates when you resize or rotate. It does not reprogram GPU scaling, unlock hidden modes, or read EDID model strings from the glass. Guidance reminds you that DevTools docks, sidebars, mobile URL bars, and pinch zoom on phones change viewport numbers without changing physical panel resolution. Multi-monitor workflows need the browser window on the suspect display before trusting screen fields. Listeners on resize and orientationchange refresh numbers when docked laptop lids open or when iOS Safari shows or hides bottom bars. Outer window dimensions may include toolbars depending on what the browser exposes to script, copy field labels exactly into tickets rather than paraphrasing screen size. Visual viewport height when shown can differ from layout viewport height during pinch zoom on supported mobile browsers. matchMedia queries are not evaluated here; numeric sizes help CSS authors more than boolean breakpoint flags alone. ” Projector overscan cropping affects perceived layout viewport on cheap HDMI projectors, geometry readout still reflects browser belief, not bezel crop. Mobile dynamic toolbars shrink innerHeight when users scroll, capture viewport after UI settles, not on first paint with chrome expanded.

When to use it

Use Screen Resolution when filing layout bugs, verifying HiDPI screenshot dimensions, checking classroom projector viewports, comparing phone landscape versus portrait after rotation, and confirming kiosk browsers are not stuck at unexpected zoom. Prefer Device Information in Hardware for touch points or concurrency beside geometry. Prefer Display Aspect Ratio Test when you care about 16:9 versus 21:9 labeling. Prefer Browser Information when feature support at a given size is the question. After changing Windows display scaling or macOS resolution presets, reopen the page on the affected display. Use when a media query at 768px triggers unexpectedly on a tablet, record viewport width at failure time. Use when screenshot bug reports include wrong dimensions because OS scaling was 150% during capture. Use before blaming a framework breakpoint constants when the real issue is browser zoom at 110%. Foldable posture changes can fire rapid resize bursts, pause until readout stabilizes before attaching screenshots. Linux Wayland fractional scaling produces devicePixelRatio values that surprise Windows-trained support agents, include window manager name when escalating. Projector overscan cropping affects perceived layout viewport on cheap HDMI projectors, geometry readout still reflects browser belief, not bezel crop.

How it works

devicePixelRatio representing the ratio of physical pixels to CSS pixels on the current display. Visual viewport APIs may further split pinch-zoom behavior on mobile. DeviceHub reads these locally; it cannot see the monitor native timing table when the OS scales the desktop. Iframes report iframe viewports, not top-level page geometry, test at the level where the bug occurs. Remote desktop sessions report the remote client geometry, which confuses debates about a user home monitor, measure locally when native panel mode is the question. devicePixelRatio multiplies CSS pixels to physical pixel counts conceptually, useful for canvas backing store sizing debates even though this page does not allocate canvases. width often reflects the monitor hosting the window, not the union of all displays, move windows deliberately. No Permissions API grant is required for reading sizes. Projector overscan cropping affects perceived layout viewport on cheap HDMI projectors, geometry readout still reflects browser belief, not bezel crop.

Step-by-step instructions

1. Open Screen Resolution on the target display with browser zoom at 100% and DevTools undocked if chrome would skew viewport numbers.
2. Record screen, window, and viewport fields separately so tickets do not conflate marketing panel resolution with CSS layout size.
3. Note devicePixelRatio alongside OS display scaling because HiDPI multipliers explain many blurry-or-huge UI complaints.
4. Resize the window or rotate the device and confirm values update before capturing a final screenshot of the readout.
5. Open Device Information in Hardware if you also need touch, concurrency, or related hardware hints beyond layout width and height.
6. When filing alongside Browser Information, paste Screen Resolution numbers into the same ticket section labeled layout so engineers do not confuse engine version with viewport width.

Common problems

Marketing 4K labels disagree with CSS pixels under 150% or 200% Windows scaling. Browser zoom at 110% silently skews layout math. Mobile dynamic toolbars make height flicker until the URL bar settles. Dual-monitor mixed DPI reports surprising screen values when the window sits on the wrong display. Assuming Screen Resolution equals EDID native mode leads to false RMA claims when the OS downscales. Fullscreen games are irrelevant, this page measures the browser window path. Remote support viewing a user shared screen sees the agent resolution, not the user, ask the user to read numbers from their own tab locally. Browser DevTools device emulation fakes metrics, disable emulation for honest hardware reads. Projector overscan cropping affects perceived layout viewport on cheap HDMI projectors, geometry readout still reflects browser belief, not bezel crop.

Privacy explanation

Screen and viewport metrics are computed locally for display on the page. DeviceHub does not upload your dimensions for advertising profiles. No camera or microphone access is involved. Closing the tab ends listeners tied to resize events. Shared PCs can run the check freely; copy values into tickets only when needed. Window size leaks are already script-visible on any site; this page does not increase exposure beyond ordinary geometry APIs. Projector overscan cropping affects perceived layout viewport on cheap HDMI projectors, geometry readout still reflects browser belief, not bezel crop.