Some monitors have firmware bugs and don't react well to DDC commands.

You may first try to increase the DDC Sleep Factor to Medium or Long:

If the problem persists even with the DDC Sleep Factor set to Long, you will need to disable DDC completely.

To do that, disable Hardware (DDC) controls from the gear ⚙️ icon menu:

Lunar will fallback to adjusting brightness and contrast in software using Gamma values.

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Notes about Gamma:

• Conflicts with other apps that use Gamma like f.lux so you have to quit them
  • Night Shift is a good alternative as it doesn't use Gamma
• Can only lower the brightness, not increase it
  • That's why you have to manually set the monitor brightness and contrast to maximum using its physical buttons
• Can't change the volume or input of the monitor
  • Those features require DDC

Some monitors don't accept DDC commands (which Lunar uses to control brightness) so the monitor brightness will stay the same no matter what Lunar will try.

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HDMI-to-USB-C Cables

Some users report that DDC controls are blocked on specific monitors when using HDMI to USB-C cables and that switching to DisplayPort fixes their problem.

If possible, try a DisplayPort to USB-C cable.

Known to work cables

• Amazon.de: USB-C to DisplayPort Cable [email protected] 3M/10Ft [email protected]/144Hz/120Hz [email protected] [email protected]

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Smart Monitors

In most cases, DDC is blocked by a monitor setting that tries to take complete control of Brightness, Contrast or Volume.

Usually disabling those functions in the monitor settings will allow Lunar control brightness.

Below are some settings that are known to block DDC, grouped by monitor vendor.

Samsung

Note: DDC seems to be unresponsive on M7/M5 Smart Monitors even after disabling all the below features. There is no currently known solution for those monitors for now. You'll have to rely on Lunar's fallback controls.

• Input Signal Plus
• Magic Bright
• Eye Saver Mode
• Eco Saving Plus
• Smart ECO Saving
• PIP/PBP Mode

Dell

• Uniformity Compensation
• Preset Mode (this option should be set to Custom or Standard to allow DDC)

LG

• Uniformity
• Auto Brightness
• Picture Mode (this option should be set to Custom or Standard to allow DDC)

BenQ

• Bright Intelligence
• Bright Intelligence Plus or B.I.+
• Picture Mode (needs to be set to Standard)

Lenovo

• Local Dimming
• HDR
• Dynamic Contrast
• Color Mode (needs to be set to Custom)
• Scenario Modes (needs to be set to Panel Native)

Xiaomi Mi Monitor

• Dynamic Brightness
• Smart Mode (needs to be set to Standard)

PRISM

• On-the-Fly Mode (it should be set to Standard to allow DDC)

Others

• Ambient Light Sensing
• Dual DisplayPort
• Dynamic Picture Mode (this option should be set to Custom or Standard to allow DDC)
• Color Presets (this option should be set to Custom or Standard to allow DDC)

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DDC blockers

Other cases where DDC will not work:

• TV working as monitor
  • TVs don't support the VESA Monitor Control Command Set which is needed for sending DDC requests
• DisplayLink
  • DisplayLink uses proprietary drivers and while it has support for DDC, that functionality is not provided on macOS
  • Lunar can control DisplayLink monitors using the Network Control feature
• HDMI on Mac Mini
  • The Mac Mini's HDMI port blocks DDC requests without a known cause
  • Using the Thunderbolt connector fixes this (through USB-C-to-HDMI cable, Thunderbolt hub, etc.)
• Non-compliant hub/dock/adapter
  • This is the most common issue and it can't be fixed in software
  • Because most new Macs only have USB-C ports, most users use some kind of Thunderbolt hub or dock
  • A lot of these hubs block DDC requests completely,
  • If the hub supports more than one monitor, it usually forwards DDC requests to only one of them
  • Here are some of the hubs that are known to work:
    • Baseus HDMI, USB-C PD, 3 USB-A
    • Baseus HDMI, USB-C PD, 3 USB-A + Ethernet
    • Baseus HDMI, USB-C PD, 3 USB-A + Ethernet + SD/microSD reader
    • VANMASS HDMI, USB-C PD, 3 USB-A + Jack + USB-C Data + SD/microSD reader

If Lunar doesn't fallback automatically to a working control mode, you can manually disable Hardware (DDC) controls from the gear ⚙️ icon menu:

Lunar will fallback to adjusting brightness and contrast in software using Gamma values.

Notes about Gamma:

• Conflicts with other apps that use Gamma like f.lux so you have to quit them
  • Night Shift is a good alternative as it doesn't use Gamma
• Can only lower the brightness, not increase it
  • That's why you have to manually set the monitor brightness and contrast to maximum using its physical buttons
• Can't change the volume or input of the monitor
  • Those features require DDC

The active monitor hotkey behaviour was changed because a lot of users requested it.

Basically, Ctrl+Brightness is now the way to control the external monitor as that is also how macOS works natively with Ultrafine and Thunderbolt monitors.

You can still go back to the old behaviour (mostly) by setting the Brightness keys adjust in other modes dropdown to Display with cursor:

Lunar needs Accessibility permissions to listen for Media Keys (brightness and volume).

To make sure the permissions are enabled, launch System Preferences->Security & Privacy and check if Lunar is present and enabled in the Accessibility list.

If it is, try removing it and re-adding it just be sure it isn't a code signing issue.

If the keys still don't work, it's possible that:

• the F14/F15 as brightness keys option is disabled and the keyboard used doesn't send brightness key events
  • enable the option on the Hotkeys page to allow Lunar to listen for default brightness key events
• the system permissions database is corrupted
  • Launch Terminal.app and run the following command: tccutil reset All fyi.lunar.Lunar
  • Reboot the system, launch Lunar again, then give Lunar permissions when it asks
• your monitor doesn't support brightness/volume control

To check why brightness doesn't work, try running diagnostics by clicking on Open Lunar Diagnostics from the Lunar menu.

These are some of the cases where volume control is not available:

• If you see Software Control under your monitor name in Lunar
• If DDC is not responsive because of a non-compliant hub/dock/adapter (Lunar should prompt you about that)
  • In this case you could try a different way to connect the monitor to your Mac

Lunar needs Accessibility permissions to know where the windows of an app are placed.

To make sure the permissions are enabled, launch System Preferences->Security & Privacy and check if Lunar is present and enabled in the Accessibility list.

If it is, try removing it and re-adding it just be sure it isn't a code signing issue.

If offsets still don't work, it's possible that the system permissions database is corrupted (see fix here)

Unfortunately most monitors don't offer a way to hide their volume indicator OSD.

But Lunar offers a way to hide the macOS volume OSD so that at least you can see only one volume indicator.

Toggle the macOS Volume OSD setting to Hide inside the Lunar display settings

These are monitors that were connected before to your Mac but are not connected at the moment.

If you see the same monitor multiple times in both connected and not connected states, that means the macOS system assigned a different Display ID to the monitor.

This usually happens when you connect the monitor to a different port on your Mac.

From Lunar's perspective, that new Display ID looks like a completely different monitor, so it has to store a new monitor, and keep the old one around in case that Display ID reappears.

Lunar stores those monitors so that the next time you reconnect them, they will have the same settings you adjusted while they were connected. That includes:

• Min/Max Brightness/Contrast
• Gamma configuration
• Enabled Controls
• Adapt Automatically toggle
• Input Hotkey
• Locked Brightness/Contrast
• Sync Mode Role
• DDC Limits

You can click on the Not connected text to remove the monitor if you don't need it anymore.

These are system settings and are not honored by any macOS app

Lunar (and all other apps) have to listen for brightness keys explicitly and the above settings don't have any effect on apps.

To disable Lunar's own media keys listener, uncheck F14/F15 as brightness keys on the Hotkeys page.

Note: not all keyboards have brightness keys that send non-F14/F15 key events.

Re-check the checkbox if brightness keys stop working after unchecking it.

Corrupted permissions database

First thing to try is to reset the System's permissions database.

Launch Terminal.app and run the following command:

Note: to run a command, paste the text in the Terminal and press Enter after that

tccutil reset All fyi.lunar.Lunar

Then reboot the system and launch Lunar again.

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If you get a message saying you don't have permissions to do the above, you can try resetting all permissions:

tccutil reset All

Note: This will reset the permissions for all apps on the system.

And as a last resort, you can delete the whole permissions database using the following steps:

1. Open Finder
2. Go to /Library/Application\ Support/com.apple.TCC
3. Find TCC.db and move it to Trash

Then reboot the system and launch Lunar again.

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Wrong app location

Where Lunar is launched from matters.

If you, for example, launched Lunar from Downloads and gave it permissions then, and then you moved it to Applications, then those permissions are not valid.

The macOS system stores permissions based on path and code signature.

You have to manually remove Lunar from the Accessibility list and add it again from the path you always launch it.

When a Mac device sends a command to a monitor through DDC, the whole system has to pause until the monitor replies.

Some monitors have very slow response times, and some don't respond at all.

If you enabled Refresh values from monitor settings or Smooth Transition, your system might freeze or be very slow because of one of those slow monitors.

Try disabling them from the Lunar UI if possible:

If your system is constantly freezing and you can't disable those options in the Lunar UI, try doing the following steps in Safe Mode:

• Make sure Lunar is not running
• Open Terminal.app
• Run the following commands
  • defaults write fyi.lunar.Lunar refreshValues 0
  • defaults write fyi.lunar.Lunar smoothTransition 0
  • defaults write fyi.lunar.Lunar brightnessTransition 0
• If the above doesn't work, you can reset Lunar settings by deleting the following file:
  • ~/Library/Preferences/fyi.lunar.Lunar.plist

When the screens wake, Lunar forcefully re-applies the brightness and contrast values to all monitors to avoid a mismatch between what's in the UI and the actual monitor values.

This can cause lag if monitors take longer to respond or the monitors might behave in weird ways if the re-apply happens at the same time as the macOS display reconfiguration process.

You can disable this behaviour from the Advanced settings screen by unchecking the following checkbox (see the image below):

The Persistent IDs problem

For Lunar to be able to store settings for a monitor (name, brightness, input hotkey, etc.), it needs a way to uniquely identify that monitor through disconnects and reconnections.

The problem is that macOS doesn't always offer such a persistent ID.

So Lunar has to find workarounds, like reading the firmware data of the monitor, and computing a number from it that can be used as an ID.

The problem is that monitors of the same model usually have the exact same firmware data.

So if you, for example, use two monitors of the same kind, that computed ID is the same for both, so it is not unique and can't be used.

This leads to Lunar storing settings for a monitor with an ID that can:

• Disappear completely when the monitor is disconnected/sleeping
  • This causes the monitor to be shown with default settings in Lunar the next time it connects
• Be reassigned to a different monitor
  • This causes the settings to be assigned to the wrong monitor

Unfortunately this problem is not yet solvable, but I'm actively looking into anything that can help work around this limitation.

Sync Mode only syncs the built-in display of a MacBook/iMac to the external monitors. Not the other way around.

In fact, Lunar doesn't control the built-in display in any way. Whenever you use the brightness keys or the Touchbar to adjust the built-in display, Lunar simply ignores that event and the macOS system does the work.

The reasons for this are the following:

• This allows Lunar to take advantage of the built-in light sensor of a MacBook
• There is no public API for changing the built-in display brightness
  • There is a private API but it can screw up the response curve of the light sensor
  • It's not easy or obvious how that response curve could be reset (an SMC reset might be needed)
• If you have more than one external monitor, it would not be clear which one to use as a source for syncing

Display Data Channel

For most monitors, Lunar uses DDC (Display Data Channel) to read data or send commands directly to the monitor.

Examples of DDC commands:

• set brightness to 30 (or any value between 0 and 255)
• set contrast to 15 (or any value between 0 and 255)
• set volume to 80 (or any value between 0 and 255)
• mute audio
• switch input to HDMI 2
• power off (power on is not possible because a powered off monitor does not accept any commands)

After Lunar sends a DDC command, it's up to the monitor firmware to do something with that command.

Lunar can't know if, for example set brightness to 50, did actually cause a brightness change in the monitor.

Some monitors don't accept DDC in some cases and can react in a few various ways to DDC commands:

• Ignore the command and do nothing
  • e.g. you change the brightness value in Lunar but the monitor doesn't change at all
• Crash, lose video signal, turn off
  • see here how to disable DDC in that case: Bad DDC issue
• Flicker green screen or weird colors
  • disabling DDC is the only solution here as well: Bad DDC issue

Lunar also doesn't have any control on the monitor OSD so if brightness or volume appears as changing in both macOS and monitor OSD, that's just how your monitor works and can't be changed.

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Apple DisplayServices

Apple vendored displays get special treatment as Lunar uses an implementation hidden inside macOS Display Services to control them natively. The list of Apple displays include:

• Pro Display XDR
• LG Ultrafine
• Thunderbolt Display
• LED Cinema (when connected via USB)

You can see when Lunar uses this method when you see Native Controls written under the monitor name in the Lunar window.

The DisplayServices method doesn't use DDC for brightness, it uses a proprietary protocol implemented by Apple through USB (as opposed to I2C for DDC).

Contrast, volume, input and power will still be controlled through DDC as DisplayServices only supports brightness changing.

Media Keys

Media Key events are sent when the checkbox for Use F1, F2, etc. keys as standard function keys on external keyboards is not checked and you press:

• F1/F2 (brightness)
• F10/F11/F12 (volume)
• Touchbar buttons for brightness and volume
• Touchbar slider for brightness when using Lunar's Sync Mode

Media Keys also need Accessibility permissions to be enabled for Lunar, while simple hotkeys can work without that.

Hotkeys

Simple hotkeys are what you can configure on Lunar's HOTKEYS page under the Function Keys section. These don't need special permissions.

If you haven't checked the checkbox for Use F1, F2, etc. keys as standard function keys on external keyboards, you will have to hold Fn when pressing hotkeys that contain function keys like F1, F2 etc. Otherwise, something like Command+F1 will actually send Command+Brightness which is a Media Key.

If you see the Software Controls tag under the monitor name in the Lunar UI, then Lunar can't use DDC to control this monitor.

Lunar can approximate a decrease in brightness by changing the software gamma tables to make the colors look darker.

This doesn't change the hardware brightness as DDC does and can only decrease brightness, not increase it.

You have to manually set the monitor's brightness and contrast (using the monitor physical buttons) to the highest possible values that look good for your monitor.

Yes, it is a known issue.

The MacBook display can increase the brightness on isolated local regions, which is the case when rendering HDR content.

The problem is that the system reports the highest brightness of the built-in display, not an average.

So even if the display contains only a small HDR-extra-bright-white square, Lunar receives that brightness from the system, and sends it to the external monitors.

You can read more about this here: https://prolost.com/blog/edr

Also, I have no idea how to fix this.

I tried to include the local cloud cover into the Location Mode algorithm but failed because of multiple reasons.

• Weather APIs are expensive
  • Location Mode computes brightness and contrast every minute, doing an API request per minute, per user, would add up to a lot of requests
  • I tried implementing some caching mechanism but it didn't help much
• Cloud Cover percentage can be quite irrelevant
  • On some days, I would get a 95% cloud cover yet it was sunny where I standed
  • This can happen if the weather station sensors are not close to your specific location
• Factoring in cloud cover is hard
  • The way the current algorithm is written doesn't allow for adding additional factors easily
  • A major refactor would be needed to make this work

If you can't use Sync Mode but would like your monitors to better react to the changes in the ambient light around you, you could try Sensor Mode.

If you use one of Lunar's adaptive modes (Sync, Location, Sensor), you can simply decrease the brightness/contrast of the brighter monitor until it looks the same as the other one.

You can use Shift+Brightness keys to adjust only the active monitor when the MacBook lid is closed, or use the Lunar UI otherwise.

Lunar will learn from that manual adjustment and try to match the monitors better in the future.

If the discrepancy appears again, just keep adjusting the brighter/darker monitor until Lunar has enough data to match a perfect curve.

This usually happens if you use identical monitors which have the exact same firmware data. Lunar tries to differentiate between them using multiple workarounds but it can still fail.

This can also happen if you use a Thunderbolt hub with two or more monitor connections. Most of these hubs forward DDC messages to only one of the monitors.

Finally, it's possible that the not-working monitor is connected through a non-compliant adapter.

Check the Non-compliant hub/dock/adapter section in this question for more details.

Yes, Lunar can do that using a feature called BlackOut.

Read more about it here: https://lunar.fyi/#blackout

This happens in rare cases and the cause is still unknown.

To fix the issue, restart your computer.

The system will revert automatically to the last known good resolution.

Usually after restarting, the orientation/resolution controls in Lunar start to work reliably.

Accessibility Permissions are needed for the following features:

• Media Keys (listening for brightness/volume key presses)
• App Exceptions (applying offsets based on what app is visible on each monitor)

Lunar has to tap into the global key events pipeline to know when a brightness or volume key has been pressed.

Brightness and volume key events are always global, not dispatched to the currently active app like other keys.

This means there's no way to listen to brightness/volume keys in a private way, but there's no privacy issue here as Lunar only cares about the following keys:

• Brightness Down (or F1)
• Brightness Up (or F2)
• Audio Mute (or F10)
• Volume Down (or F11)
• Volume Up (or F12)

All the other key events are ignored by Lunar.

If you don't need the Media Keys functionality, you can simply deny the Accessibility permissions and Lunar won't ask again.