Issue Description
Mac fails to output video when connected via HDMI.
Common Causes
- Incompatible adapter
- Resolution mismatch
- Display detection issue
Step-by-Step Solution
Step 1: Check HDMI Adapter
- Use Apple-certified USB-C → HDMI adapter
- Avoid cheap third-party adapters
Step 2: Force Display Detection
- System Settings → Displays
- Hold Option → click Detect Displays
Step 3: Adjust Resolution
- Select external display
- Choose Scaled → Default for Display
Step 4: Restart with HDMI Connected
- Shut down Mac
- Connect HDMI
- Power on Mac
Explore Further
- Reset NVRAM (Intel Macs)
Prevention & Best Practices
Use direct HDMI cables when possible.