Match brightness across different monitors

Make two monitors follow a similar brightness level when you adjust one screen. Equal percentages can look different on different panels. This tutorial compares percentage-based synchronization with matching calculated brightness in nits. Nits matching works best when BetterDisplay has reliable minimum and maximum brightness values for each display.

Before you begin

Use two connected physical displays whose brightness sliders already work independently in BetterDisplay. Each needs a working brightness controller. Adding a display to a group does not provide brightness support. If you rely on DDC, use a connection that already supports working brightness adjustments. Resolve an unresponsive slider before attempting synchronization.

Choose one display as the source: the screen whose slider you will normally adjust. The other is the target, which receives its changes. Keep each display’s picture mode unchanged and use stable viewing conditions throughout the comparison. Start with SDR content and leave HDR and brightness upscaling out of this first comparison. Temporarily pause automatic brightness or other brightness automation if it would keep changing the levels during your test.

Note the current brightness of both displays and any synchronization rule you plan to change. Check other active groups for brightness rules involving these displays. Pause competing rules while comparing so one source adjustment follows one predictable path.

Before entering manual nits values, note any values you previously saved yourself. The sheet can also show automatic estimates, so a visible number is not necessarily a saved override. If you need a record of the existing configuration, export it with Settings > Application > Advanced Settings & Privacy… > Manage App Settings > Export…. See backing up app settings.

Choose one source and its receivers

1. Open Settings > Groups and select Default Group, or an existing display group that contains both displays. Confirm that both are members and that its Activation section reports Display group is currently active. If it is inactive, resolve its membership or activation rules using Individual group.
2. Open Synchronization Settings. If a Brightness entry already exists, open it and switch Synchronize Brightness off while you set it up. Otherwise choose Add New Synchronization… > Brightness, then switch it off during setup. Choose the general Brightness entry. The separate hardware, software and combined entries do not offer the nits option used here.
3. Switch Any group member can be a sync source off. Leave Source member must be an external display, Source member must be an Apple display and Source member must be set as the main display off. Enable Source must be on the list of specified members, then select only your chosen source under Sync source group member displays. Enabled source filters are combined, so an extra filter could reject the screen you selected.
4. Switch All group members are sync targets off. Under Sync target group member displays, select only the physical SDR displays that should follow the source. Leave the source and unrelated displays unselected. When you choose targets individually, the exclusions used by automatic target selection do not apply.
5. Leave Synchronize changes triggered externally off for now. Switch Synchronize brightness nits off, switch Delta syncing off, and leave Consider range differences on. Turn Synchronize Brightness on. Use the back arrow to return to the list and turn Enable synchronization for this display group on.

The rules are saved without an Apply button or restart. Let the settings settle, then make a fresh adjustment with the source display’s Brightness slider in the App Menu. Do not hold Shift: it bypasses synchronization for that adjustment. This first configuration sends an absolute position within the source’s range to the corresponding position within each target’s range.

Route brightness from Built-in Display to FlipAction Pro with explicit source and receiver lists.

Compare comfortable low, middle and high positions without pushing either display to an uncomfortable level. Note how the receiving screen follows the source, and whether the pair still looks noticeably different. Their displayed percentages may differ if their configured ranges differ. Compare where each sits within its available range. Delta syncing is normally on for a new entry, but would preserve an initial difference rather than give you a direct comparison of range positions.

Give each display reliable luminance anchors

BetterDisplay needs a brightness range for each display to calculate nits. Use reliable SDR specifications or measurements at the minimum and maximum hardware brightness settings in your usual picture mode. If you do not have better values, keep the existing estimates rather than guessing. An advertised HDR peak for a small highlight is not the maximum brightness of an ordinary SDR desktop.

1. Switch Synchronize Brightness off while reviewing the anchors. Open Settings > Displays > [display] > General Settings > Configure Brightness Nits Ranges… for the source.
2. Review Hardware control - minimum and Hardware control - maximum. They describe estimated luminance at the hardware brightness endpoints. When hardware brightness is unavailable or disabled, the maximum also provides the brightness basis for software adjustment. If the automatic basis is appropriate, leave its fields unchanged.
3. If you have credible replacement endpoints, enable Manual nits range configuration and enter only those verified values. Keep the minimum below the maximum. Press Return or leave each field to commit it, then recheck both fields: entering a minimum above the maximum, or a maximum below the minimum, can change both fields. Clearing a field removes its override. Escape discards an edit before it is committed.
4. If present, leave HDR mode - peak SDR brightness and HDR mode - peak HDR brightness unchanged for this SDR comparison. They describe separate HDR-related anchors, not substitute SDR hardware endpoints. Close the sheet with Done and repeat the review for every target.

FlipAction Pro’s existing 7–450 nit range is unmeasured. This sheet shows where to enter verified endpoints for the active picture mode.

These changes save directly. Closing the sheet does not cancel committed edits. Turning Manual nits range configuration off ignores saved overrides without deleting them. You can therefore return to the automatic basis and later re-enable your saved values. See the brightness-anchor reference for the automatic estimates and conditional HDR fields.

Switch to calculated nits matching

1. Return to Settings > Groups > [group] > Synchronization Settings > Brightness. Keep the same source and target selections, enable Synchronize brightness nits, and enable Synchronize Brightness.
2. Confirm that the delta and range options disappear while nits mode is active. The target now receives the source’s calculated nits value instead of its percentage position.
3. To compare the displayed estimates, open Settings > Menu > Menu Appearance & Behavior, enable Show slider labels and values, then enable Show brightness slider nits values. In each participating display’s General Settings, also enable Show brightness nits. Supported brightness sliders can then show nits alongside their percentages.
4. Let the setup settle and make a fresh source-menu slider adjustment. Repeat the low, middle and high comparisons you made earlier. Keep the content and picture modes unchanged so you are comparing the two synchronization methods under the same conditions.

Enable calculated-nits synchronization after configuring credible ranges. The current unmeasured estimates do not verify equal panel luminance.

Check the result

The selected receivers should follow a new source adjustment, while unrelated displays stay unchanged. The two percentages may differ because each display converts the same calculated luminance into its own brightness setting. Matching nits estimates show that the calculation is working. Compare the screens too, since equal estimates do not guarantee equal measured or perceived brightness.

Compare several levels within the displays’ common usable range. If the source requests a level that a target’s active brightness path cannot reproduce, that target reaches its available limit instead of continuing to match. Hardware brightness alone cannot go below or above its endpoints. Combined brightness can also use supported software dimming or upscaling. The useful matching range depends on those available methods.

If the screens track more usefully across the range, keep the nits rule. If they only agree at one level, revisit the endpoint evidence and picture settings. White balance, contrast, HDR behavior and the content itself can still make two screens look different. This is brightness matching, not color calibration.

Optionally follow detected external changes

After the source-slider test succeeds, enable Synchronize changes triggered externally if you want detected changes from automatic brightness, Touch Bar or Control Center to drive the receivers too. Leave Synchronize external changes only off to keep your ordinary app adjustments working as sources. Both options start off for a new entry.

The source controller must be able to detect the outside change. Enabling the option does not add that capability. Check that the source’s value changes in BetterDisplay, then that the receivers follow. Applicable rules can also reconcile brightness after a display configuration change using an eligible Apple display with automatic brightness. See automatic external brightness for the detection requirements.

Troubleshooting

• The source changes but the target does not: check that the group is active, both synchronization switches are on, the chosen source passes every enabled filter, and the connected target is selected. Confirm that the target’s own slider still works. If only app changes fail, turn Synchronize external changes only off. See Synchronization Settings.
• Brightness keys produce a different result: keyboard targeting set to All suitable screens adjusts those displays directly and bypasses group brightness synchronization for that operation. Use the chosen source’s App Menu slider to test this rule. Holding Shift during a slider adjustment also bypasses synchronization. It does not teach a matching curve.
• The nits option is missing or unavailable: use the general Brightness entry, and check the Pro requirements below. An entry for Brightness (Hardware), Brightness (Software) or Brightness (Combined) is a different choice.
• The displayed nits match but the panels look different: verify the saved anchors, active brightness controllers and unchanged picture modes. Recheck any automatic brightness, software dimming, HDR or upscaling that returned during testing. See why nits estimates differ from expectations. Use reliable values when changing the anchors.
• A target stops following near one end: compare within the overlap of the active brightness paths’ usable ranges. Changing an anchor does not overcome a panel or controller limit. If behavior changed after enabling HDR or selecting an Apple reference preset, repeat the comparison in the original mode before deciding whether different anchors are justified.

Undo the matching setup

1. Switch Synchronize Brightness off before restoring either screen. If you added the entry solely for this test, choose Remove Synchronization… > Remove to delete that entry and its settings. If it existed before, restore its recorded settings rather than removing it.
2. Restore each display’s saved nits overrides and the original Manual nits range configuration state. Clear only fields that originally had no override. Restore both endpoints after any automatic clamping, plus any HDR anchors you changed.
3. Restore the earlier brightness of each display. Stopping synchronization leaves their current brightness in place. Resume any automatic-brightness or other automation you paused.
4. If you edited an existing rule, restore its source, targets and synchronization options. Restore the group-wide switch and any other rule you paused. You can keep the nits labels visible, or turn the display preferences back off. Re-enable the original brightness rule last.

If you exported settings, use the backup as a record for values you need to restore. Importing it replaces the whole app configuration and requires a restart. That is a separate recovery action explained in the backup reference.

Related pages

• How can I keep two displays at similar brightness?
• Why does BetterDisplay’s nits value differ from the brightness I expect?
• Synchronization Settings
• Brightness nits ranges

Additional information

This section explains the license and platform requirements for the matching workflow.

Features requiring Pro license

Synchronize brightness nits and editing individual source/target selections require Pro or an active trial. Custom-group synchronization also requires Pro. Basic general Brightness synchronization in the Default Group does not require Pro. Manual nits-range configuration and nits-display preferences do not independently require Pro.

Platform compatibility

This workflow is available on Apple silicon and Intel Macs, with usable brightness controllers on the participating displays. The documented BetterDisplay build requires macOS 26.3 or later. Controller and connection support determine hardware brightness and external-change detection. Software adjustment, HDR and Apple preset behavior depend on the display and its active configuration. No Screen Recording permission is required for this group-matching procedure.