Browser Display Diagnostics

How to use Browser Display Diagnostics

Read one local CSS screen, window and viewport snapshot with device-pixel ratio and optional fixed media-query checks when you explicitly run the tool. Distinguish browser-exposed CSS dimensions from physical panel resolution. Resize or zoom and run again to compare the current context; no listener, account, permission prompt or hardware identifier is needed.

1. Provide .
2. Choose the supported mode and run the tool. Review its assumptions and any reported errors.
3. Copy the result or download a separate output; reset to clear the current form.

Good to know

• This reports browser-exposed Screen, Window, document client and optional VisualViewport values in CSS pixels, plus DPR and screen orientation if exposed. These are observations of the current browser context, not an independent measurement of physical display pixels, size, panel PPI, calibration or hardware identity.
• The browser may hide, round or report virtual screen data. Window/page zoom, pinch zoom, scrollbars, a mobile keyboard, display changes or headless/emulated testing can change the result. There is no reliable derived physical resolution or device-model claim.
• One explicit Run reads a fixed bounded set of dimensions and, optionally, 14 predefined media queries. No user-supplied expression/query is evaluated, no continuous resize/device listener installed, and no camera, microphone, geolocation, clipboard, storage, account or permission API accessed.
• Unavailable/refused/nonfinite/negative or greater-than-10,000,000 dimensions are returned as null; positive ratio/scale values must also be greater than zero. Null is not silently converted to a working value. False fixed media-query matches are observations, not feature-support certification.
• Snapshot data appears only in the local report and optional JSON download; it is not saved or transmitted by this tool. Shared platform usage hooks, if configured separately, must remain input-free. A copied report still contains information about this browser context, so review it before sharing.
• Native browser comparisons are required for UI/platform verification. Logic tests with supplied browser-like objects do not prove actual display dimensions, native browser permissions or cross-browser behavior.
• Structured text output is limited to 500,000 characters. Reduce the supplied source when that separate output budget is exceeded.
• Inputs are processed on this device and are not automatically saved or uploaded.