What browsers expose
Resolution, device pixel ratio, colour depth, some colour gamut signals, HDR support, refresh estimates, and frame timing.
What browsers hide
Exact model, serial number, true brightness, true contrast, response time, factory calibration, and panel type are usually hidden.
Why this still helps
Mismatch between expected and observed signals often reveals settings, cable, browser, or operating system problems.
When to use hardware
Use a calibrator or lab review for colour-critical work, brightness claims, contrast, or precise response measurements.