More and more monitors with a resolution higher than full HD – but Microsoft has only optimized Windows to this level of detail. If you use a 4K display at 24-27 inches, for example, system elements and text will be so small you won’t be able to read them. The solution is to resize; this option can be found in the standard Display settings (right-click on an empty area of the Desktop to see this option in the pop-up menu).
Windows will try to guess what magnification is needed based on the resolution and mark it as the recommended value. If there is no recommended value, it’s worth setting it to 150% in the first instance so that you can decide whether it’s appropriate to adjust it up or down further based on what you see. If applicable, the optimum setting will depend on the monitor size, aspect ratio, resolution, and even the selected system theme.