Initial Screen&Window Dimensions & MediaQueries
For ALL browsers (uses every possible permutation of variable names)
Viewport constrained to device width and density -- see also with unconstrained "viewport"

To maximize correctness across the widest possible variety of hardware and software, this display presents the values as they were at the time of initial page load. After any change (for example rotating the device), the old values will continue to be presented. To see new values, manually reload this page.