Control Monitor Input Source on macOS with BetterDisplay and DDC

Alik Khilazhev — Wed, 16 Oct 2024 20:31:06 +0300

If you as me have single monitor and 2 Mac devices (for example, I have corporate Macbook and personal Mac Mini) you may want to use the same monitor for both devices. And you may want to switch between them without unplugging and plugging cables or selecting input source using monitor buttons.

In this post I will show you how to configure hotkeys for that.

Quick answer

App: Use BetterDisplay — it exposes a CLI and GUI to switch monitor inputs via DDC/CI.

When DDC/CI works: Your monitor must support the DDC/CI protocol and have it enabled. Most modern displays (Dell, LG, BenQ, etc.) support it.

When it won’t work: Some monitors, USB-C hubs, or cheap HDMI adapters block DDC signals. If BetterDisplay shows no DDC Input Sources, your hardware path doesn’t pass DDC — try a direct cable instead of a hub or adapter.

Hardware

You will need a monitor with multiple input sources. For example, I have Dell S2722QC tt has 2 HDMI ports and 1 USB-C port where:

Macbook Air connected to port HDMI-2
Mac Mini connected to port USB-C-1

Software

There is app called BetterDisplay that has a lot of powerful features. But for our case we need only one feature - change display inputs using DDC.

Install it on both Macs. You will have 14 days trial period with all PRO features.

Enable Accessibility for BetterDisplay in System Settings -> Privacy & Security -> Accessibility.

Then try to switch input source by clicking on BetterDisplay icon in the menu bar -> DDC Input Source -> Select next port.

If it works, you can continue to the next step. Otherwise check if your monitor supports DDC protocol and ensure Accessibility is enabled for BetterDisplay.

Paid option

If you are ready to pay 19$/19€ x2 for both Macs you can buy BetterDisplay. And then configure hotkeys in the app settings Settings -> Keyboards -> Custom keyboard shortcuts -> DDC Input Source.

Click “Record Shortcut” and press the key combination you want to use, for example CMD + F1 and CMD + F2.

Free option

If you like me don’t want to pay for 40$ for single feature there is a hacky way to do it.

We need an app that can handle hotkeys and run shell commands. I use skhd, Simple Hotkey Daemon for macOS and it can handle custom hotkeys. Or you can use any other app you like.

Installing skhd

brew install jackielii/tap/skhd-zig
skhd --install-service

Configuring skhd

Before configuring skhd we need to know ddc value for each input source. To do so, go to Settings -> Displays -> “Your monitor name” -> DDC Input Sources, and save IDs from Value column for each input source:

In my case it’s 18 for HDMI-2 and 25 for USB-C-1.

Then I add next lines into ~/.config/skhd/skhdrc:

cmd - f2 : /Applications/BetterDisplay.app/Contents/MacOS/BetterDisplay set -ddc=25 -vcp=inputSelect
cmd - f1 : /Applications/BetterDisplay.app/Contents/MacOS/BetterDisplay set -ddc=18 -vcp=inputSelect

And that’s it! Now you can switch input source using hotkeys CMD + F1/F2.

Skhd on alikhil