Why does BetterDisplay show a different brightness percentage than my monitor?

BetterDisplay’s brightness percentage may describe software dimming or a combined brightness scale rather than the monitor’s hardware setting. Those percentages are not necessarily the same measurement, and neither is a direct measurement of emitted light in nits.

With Combined brightness enabled, one slider can span hardware brightness, software dimming below the hardware minimum, and supported XDR/HDR upscaling. The switchover point and other range settings determine the mapping. A combined value of 50% therefore does not generally mean the monitor’s own brightness should read 50%.

If you want the main slider to use hardware brightness alone when available, open Settings > Displays > [display] > Device Control and turn off Combined brightness. Make sure a working hardware-brightness controller is actually available. Disabling combined control does not add DDC support to a connection that lacks it.

Software dimming changes the displayed image without changing the monitor’s brightness number. Returning software brightness to its neutral level removes that dimming, so the image can become brighter while the monitor’s own number remains unchanged. At full software black, raising the monitor’s hardware setting does not restore the hidden image.

If the monitor uses a hardware range such as 0–50, the app’s normalized percentage still needs the correct raw DDC range. Open Device Control > DDC Control > Configure Controls…, select brightness, and check DDC value range minimum and DDC value range maximum. Set the range supported by your monitor if detection reported it incorrectly. Do not assume every model uses 0–100. If the level resets after sleep, see reapplying DDC settings on wake.

On a Sidecar iPad, BetterDisplay’s dimming changes the displayed image. It does not adjust the iPad’s own brightness setting. Use the iPad’s Control Center when you want to change that setting. The app’s percentage alone does not establish how much power the iPad saves, which depends on its panel and displayed content.

If you want software dimming without DDC changes to the monitor, open Settings > Displays > [display] > Device Control > Add or Remove Controllers… and remove DDC Control. Software Image Adjustments remain a separate path. Removing DDC also stops its other hardware commands, such as input or volume control. It does not undo values already stored by the monitor or disable another configured hardware controller.

If you specifically selected hardware control and the monitor’s own setting still does not follow, investigate DDC communication and readback separately. Some monitors accept writes but do not provide reliable readings. See Image Adjustments and DDC control.

A monitor preset can lock hardware brightness even while DDC successfully reads its current value. If the hardware slider moves and then returns to the old value, check the monitor’s own picture preset, low-blue-light mode and HDR settings. If brightness is locked there too, switch to a preset that permits adjustment and try again. Which modes impose this restriction depends on the monitor. Changing BetterDisplay’s percentage range cannot unlock a firmware-imposed fixed level.