COM Port Monitor

A lightweight Windows utility that detects which application is holding a serial (COM) port. Built for developers, hardware engineers, and anyone who needs to quickly identify COM port conflicts.

Features

• Auto-detects all COM ports from Windows registry
• Maps COM ports to NT device names (e.g., COM4 → \Device\Serial15)
• Finds the owning process using Sysinternals handle64.exe (embedded)
• Dark mode UI — easy on the eyes for long debugging sessions
• Single-file executable — no installation, no dependencies

Use Case

You plug in a USB-to-Serial adapter, Windows assigns it COM15, but your app says "Access Denied."
COM Port Monitor tells you exactly which process has it locked — in one click.

Download

Get the latest release from the Releases page.

Requirements

• Windows 10/11 (64-bit)
• Administrator privileges (required for handle enumeration)

How to Use

1. Download COMPortMonitor.exe from Releases
2. Run as Administrator
3. Click Check All or Check on any specific port
4. See which process owns it — instantly

Built With

• C# / .NET 7
• Windows Forms (custom dark theme)
• Sysinternals handle64.exe (embedded)

License

MIT License — free for personal and commercial use.