スクリーンとブラウザの情報
画面解像度、ビューポート、デバイスピクセル比、ブラウザの詳細、ハードウェアの並行性などを表示します。
このツールについて
ブラウザのJavaScript APIで検出されたデバイスとブラウザ環境の包括的なスナップショットを即座に確認できます。画面解像度、ビューポートの寸法、デバイスピクセル比、色深度、向き；ブラウザのユーザーエージェント、言語、プラットフォーム、機能フラグ；ハードウェアの並行性（CPUコア数）、デバイスメモリ、ネットワーク接続タイプ；ページ読み込みとDOMContentLoadedのタイミングをカバーします。ワンクリックで完全なレポートをJSONまたはプレーンテキストとしてコピーできます。
使い方
- 1 ツールを開くと、デバイスとブラウザの情報が自動的に検出されて表示されます。
- 2 セクションを閲覧してください：画面、ブラウザ、ハードウェア、タイミング、機能サポート。
- 3 「JSONとしてコピー」または「テキストとしてコピー」をクリックして完全なレポートをクリップボードにエクスポートしてください。
- 4 「これはどのように比較されますか？」をクリックして、一般的なデバイスと設定の参照値を確認してください。
What your browser already knows about your device
Every web page can read a surprising amount of information about the device it is running on — not by probing your computer, but by asking standard JavaScript objects that browsers expose: screen, navigator, window, and performance. This tool simply collects those values and lays them out clearly across five panels: Screen, Browser, Hardware, Timing, and Feature Support. It is a fast way to answer "what resolution is this monitor?", "how many CPU cores does my laptop report?", or "does this browser support WebGL?" without installing anything.
Screen size has three different meanings
People say "resolution" loosely, but the tool reports several distinct measurements because they answer different questions:
| Value | What it measures |
|---|---|
| Screen width/height | The full physical screen in CSS pixels |
| Available width/height | Screen minus OS bars (taskbar, dock) |
| Viewport width/height | The actual area your browser window can draw into |
| Device pixel ratio | Physical pixels per CSS pixel (2 on a Retina display) |
The device pixel ratio (DPR) is the one most people miss. A "Retina" laptop might report a 1,512-pixel-wide screen in CSS pixels but a DPR of 2, meaning it actually packs 3,024 physical pixels across. That is why an image looks sharp on one screen and blurry on another at the same CSS size — the high-DPR screen needs an image with twice as many real pixels.
A worked example: the "compare" panel
Click How does this compare? and the tool turns your raw numbers into context. If your screen reads 1920×1080 it notes that this is standard Full HD; if your DPR is 2 or more it flags a HiDPI/Retina display; it buckets your CPU core count into entry-level, mid-range, or high-end; it labels your reported memory; and it tells you which responsive breakpoint your current viewport width falls into (mobile, tablet, or desktop). So instead of "viewportWidth: 1440," you learn that you are at a desktop breakpoint — directly useful when testing a responsive layout.
Beyond the screen: hardware, network, and features
The Hardware panel reports the number of logical CPU cores and, where the browser allows it, an approximate device-memory figure and live network details — the connection's effective type (such as 4g), estimated downlink speed, and round-trip time. The Feature Support panel runs quick checks for capabilities a developer cares about: touch input, WebGL, WebAssembly, the Notifications, Geolocation and camera APIs, Service Workers, IndexedDB, and Web Workers, each shown as a clear yes or no. The Timing panel adds your time zone, its offset, and how long the page itself took to load.
Exporting what you find
Two buttons copy the whole report to your clipboard: Copy as JSON gives a structured object you can paste into a bug report or a script, and Copy as Text gives a flat, human-readable list of key-value lines. A Refresh button re-reads everything live, which is handy if you resize the window or rotate a device and want updated viewport and orientation numbers.
Practical use cases
- Bug reports. Attach your exact screen size, DPR, browser, and feature support so a developer can reproduce an issue.
- Responsive testing. Resize the window and refresh to watch the viewport width cross breakpoints.
- Buying or comparing hardware. Confirm the resolution, color depth, and core count a machine actually reports.
- Capability checks. Verify a browser supports WebGL or Service Workers before relying on a web app that needs them.
Common misunderstandings
- Reported numbers are approximations on purpose. To resist fingerprinting, browsers round or cap values like device memory; treat them as ballpark, not exact specs.
- Viewport is not screen size. A maximized window still has browser chrome; viewport width is what your CSS media queries actually see.
- Some fields read "unknown" or "API not available." Network and memory details are only exposed by certain browsers; a blank there is the browser declining, not a fault.
Privacy
Everything is read and displayed locally in your browser. None of these values is transmitted to a server by this tool — the copy buttons put the data on your clipboard, and nothing leaves your device unless you paste it somewhere yourself.