How can I tell whether my display is already using HiDPI?

Open the display’s Display Mode submenu in BetterDisplay and inspect the highlighted current mode. A sparkle icon on that row identifies HiDPI rendering. A row without it uses LoDPI rendering.

For a worked comparison, see HiDPI versus LoDPI at the same desktop size.

Check the current row, rather than assuming that a listed HiDPI option is active. The same desktop size can appear in both HiDPI and LoDPI modes. You do not need to select another mode just to check.

HiDPI describes how macOS renders the desktop. It does not change the physical pixel density of the monitor, so a large, lower-density monitor will not necessarily look as sharp as a smaller Retina display. See HiDPI and why text may still look poor for that distinction.

If the current mode already gives you the size and rendering you want, no additional HiDPI configuration is needed. The Display Mode guide explains the other row markers.