Why does a brightness query return a different value from the monitor’s own menu?

A hardwareBrightness query returns the brightness value tracked by BetterDisplay on its own percentage scale. It does not perform a fresh DDC read from the monitor, so it can differ after you change brightness using the monitor's physical buttons.

To request the monitor's actual DDC luminance value and reported maximum, use:

betterdisplaycli get -name="Desk Display" -ddc -vcp=luminance -value -max

Replace Desk Display with your display's name. This requires an enabled, supported DDC controller and a monitor/connection that supports reading that feature. Some displays accept brightness commands but cannot return a usable value. A failed read therefore does not always mean that writes will fail.

For ongoing synchronization, open the display's Device Control > DDC Control > Configure Controls… settings. Select brightness and enable Periodically read and update current value from display for brightness, if reads work reliably. Readback is off by default. See DDC Control for frequency and feature configuration.

Also distinguish brightness from hardwareBrightness. The main brightness feature can combine hardware and software adjustment. Its percentage may differ from the percentage on the monitor’s hardware slider. Direct DDC uses the monitor’s raw range, which may be larger or smaller than 0–100.

After writing a value, query DDC directly or check the monitor’s own menu to confirm the result. Querying hardwareBrightness checks only the app’s tracked value. See direct DDC examples.