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When designing for the web it’s easy to forget that cross-browser testing is only half the story. Variations in hardware and operating system can have just as much to say. There’s a panoply of possible platforms — all with their own inputs and outputs, quirks and constraints. Sometimes the only way to handle the «other»-slice of the hardware pie is a healthy dose of technical restraint.

For example, consider the differences between a 27″ desktop monitor with 2560 × 1440 px at 144 Hz, and a 13″ HiDPI laptop screen with 1440 × 900 px at 60 Hz. While both may be amazing displays, neither can handle any design.

When it comes to animations, the desktop monitor has the upper hand. Its high refresh rate and low DPI will render any hardware accelerated animations buttery smooth. On the other hand, a laptop with a high DPI screen and an integrated GPU will often turn non-trivial animations into spinning fans.

When it comes to text, a high DPI laptop running macOS can make any font look good. However, many of these same fonts will not be optimized for the low DPI of the desktop monitor. When combined with how Windows renders fonts the result can look a weight off, a shade off, or even like anti-aliasing is turned off.

When it comes to viewport space, the desktop has plenty. But few sites have good support for a 2560 px wide window. On a 1440 × 900 px laptop you’re left with an effective viewport height of about 800 px after the operating system and browser have taken their toll. There’s little room left for a fixed header.

Critically, you cannot get a feel for these differences in a virtual machine. You need the actual hardware. So, if resources for cross-hardware testing are limited, keep it simple. Constrain keyframes to transform and opacity. Remember that font-family: system-ui is always an option. And when it comes to viewport size, make sure to be responsive in both width and height.

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