System and device info tests

Screen size is two numbers, not one

Ask what resolution a device is and you get two different honest answers. There is the CSS pixel size the browser lays out with, and the physical pixel size the panel actually has. The ratio between them is the device pixel ratio, and on modern phones and Retina laptops it is 2 or 3.

That gap explains a lot of confusion. A phone advertised at 2532×1170 reports something closer to 844×390 to a web page, and both figures are correct. If you are filing a bug, sizing an image, or arguing with a designer about a layout, the CSS size is the one that matters — and it is the one this check reports alongside the ratio, so you can work back to the physical count.

The same page reports your browser and engine version, platform, and the GPU string exposed through WebGL. Support requests tend to ask for exactly that list, and copying it beats guessing.

What the battery reading covers, and what it does not

The browser exposes charge level as a percentage, whether the device is plugged in, and rough estimates for time to full or time to empty. That is genuinely useful for a quick sanity check: a laptop that says it is charging but never climbs past the same percentage usually has a charger or cable problem long before it has a worn cell.

Be clear about the ceiling, though. There is no browser access to cycle count, design capacity, or battery wear. Anything claiming to measure battery health in a web page is estimating, and you should not trust it. For real health figures use powercfg /batteryreport on Windows, System Information under Power on macOS, or Battery Health in iOS settings.

Support is uneven too. Chrome and Edge implement the Battery Status API, Firefox removed it, and Safari never shipped it — so on some browsers this check will correctly tell you the data is unavailable rather than invent a number.

None of it is collected

Every value here is read in your browser and displayed. Nothing is logged, sent, or tied to you.