DDC/CI not working through an HDMI switch or KVM
Many HDMI switches and KVMs don’t pass DDC/CI commands reliably. Here’s how to test your setup and the best alternatives on Windows.
DDC/CI commands can be dropped or altered by HDMI switches and KVMs. Even if video works perfectly, the control channel may not.
If you rely on hardware brightness control, you’ll want to verify whether your switch/KVM passes DDC/CI.
Quick test
- Connect the monitor directly to the PC. If DDC works direct but not through the switch/KVM, the switch/KVM is blocking DDC.
- Try a different input type (DP instead of HDMI) if available.
- Some switches only pass DDC on one specific port — test each port.
What to do if it doesn’t pass DDC
- Use GPU dimming for that monitor (works even when DDC is blocked).
- If you need true hardware brightness, look for a switch/KVM that explicitly supports DDC/CI pass‑through (and has real-world confirmation).
- Keep the control path simple: fewer adapters and fewer hops.
Related guides
Frequently asked questions
Why do HDMI switches and KVMs break brightness control?
Many switches/KVMs strip or emulate EDID and don’t forward the DDC/CI messages used for brightness control.
How can I confirm the KVM is the problem?
Test the same monitor with a direct cable from the PC. If DDC works direct but fails through the switch/KVM, the middle device is blocking DDC/CI.
What’s the workaround if I must use a KVM?
Use gamma dimming for a stable brightness slider, or choose a switch/KVM specifically advertised as passing DDC/CI (rare, but they exist).