COM Ports Missing in Device Manager? Fix in Windows 10

If your COM ports have disappeared from Device Manager in Windows 10, the fix usually involves re-enabling hidden devices, updating the port driver, or checking BIOS/UEFI settings. This guide walks you through the most common causes and step-by-step solutions to get your serial ports (COM1, COM2, etc.) visible again.

Why COM Ports Go Missing

COM ports are how Windows 10 communicates with serial devices like Arduino boards, GPS receivers, barcode scanners, and industrial machinery. They can vanish from Device Manager for several reasons:

Driver corruption or outdated drivers – Windows updates or third-party software can break the serial port driver.
USB-to-serial adapter issues – A faulty adapter or its driver can cause the port to disappear.
BIOS/UEFI settings – Onboard serial ports may be disabled in firmware.
Windows power management – USB selective suspend can cut power to the port.
Hidden devices – The port might be present but hidden from the default view.

Understanding the cause is the first step, but the solutions below cover all of these scenarios.

How to Check If COM Ports Are Hidden

Windows 10 hides devices that are not currently connected, but sometimes it hides them even when they are plugged in. To reveal them:

Open Device Manager (right-click the Start button and select Device Manager).
Click View in the menu bar and select Show hidden devices.
Expand Ports (COM & LPT) – if you see a port with a faded icon, it’s hidden. Right-click it and select Enable device.

If the Ports section is still missing, the port is not just hidden – it’s not being recognized at all. Continue to the next steps.

Step-by-Step Fixes for Missing COM Ports

Try these in order, as each is increasingly invasive.

1. Restart the PC and Reconnect the Device

A simple restart clears many temporary glitches. Unplug the serial device or USB adapter, wait 10 seconds, plug it back in, and check Device Manager again. If you’re using a USB-to-serial adapter, try a different USB port (preferably a rear port on the motherboard).

2. Update or Reinstall the Driver

If the port appears under Other devices as an unknown device, the driver is missing or corrupted. Right-click the unknown device and select Update driver → Search automatically for drivers. If Windows doesn’t find one, go to the manufacturer’s website for your adapter or motherboard and download the correct driver.

If the port is listed but not working, right-click it, select Uninstall device, then restart the PC. Windows will reinstall the driver automatically.

3. Check BIOS/UEFI Settings

Onboard COM ports (often called Serial Port or COM1) can be disabled in BIOS. Restart your PC and press the key shown on screen (usually Del, F2, or F10) to enter setup. Look under Advanced or Peripherals for an option like Serial Port or Onboard COM Port. Set it to Enabled, save, and exit.

4. Disable USB Selective Suspend

For USB-to-serial adapters, Windows may cut power to save energy, causing the port to disappear. Go to Control Panel → Power Options → Change plan settings → Change advanced power settings. Expand USB settings → USB selective suspend setting and set it to Disabled. Restart the PC.

5. Use Device Manager to Scan for Hardware Changes

Click the Scan for hardware changes icon (a monitor with a magnifying glass) in the Device Manager toolbar. This forces Windows to re-enumerate all devices, which often brings back the missing port.

Common Problems and Their Specific Fixes

Port appears as “COM3” but the software expects “COM1” – Right-click the port, select Properties → Port Settings → Advanced, and change the COM port number to one that’s free.
Port is there but shows a yellow warning icon – The driver is failing. Update the driver as described above, or check if the device is in use by another program.
Port disappears after Windows Update – Windows Update may install a generic driver that conflicts. Roll back the driver via Properties → Driver → Roll Back Driver.
Multiple USB adapters cause port numbers to conflict – Each adapter gets a unique port number; if you plug one into a different USB port, it may get a new number. Use the Advanced settings to assign a fixed port number.

How to Prevent COM Ports from Vanishing

Once you’ve restored your COM port, a few habits reduce the chance of it disappearing again:

Always eject USB devices safely before unplugging.
Keep your motherboard and adapter drivers up to date.
Disable USB selective suspend globally if you use serial adapters often.
Assign a fixed COM port number in Device Manager for devices you use regularly.

When to Use a USB-to-Serial Adapter vs. Onboard Port

If your PC lacks a physical COM port (most modern laptops do), you’ll need a USB-to-serial adapter. These adapters emulate a COM port and work with most software. However, some legacy software expects a real COM port address (like 0x3F8), which a USB adapter cannot provide. In that case, you may need a PCIe serial card that adds a hardware COM port. Check your software’s documentation to see if it requires a hardware port.

Frequently Asked Questions

Why is my COM port not showing in Device Manager even after I plug it in?

This usually means the driver isn’t installed or the device is not being recognized. Check under Other devices for an unknown device, and install the correct driver from the manufacturer. If it’s an onboard port, verify it’s enabled in BIOS.

How do I find the COM port number in Windows 10?

Open Device Manager, expand Ports (COM & LPT), and you’ll see the port name like “COM3”. If the port is missing, you can also check the Device Manager → View → Show hidden devices to see ports that are not active.

Can a missing COM port be caused by a virus?

It’s unlikely. Malware usually doesn’t target COM ports. The most common causes are driver issues, disabled ports in BIOS, or hardware problems. Run a full antivirus scan if you suspect something, but focus on the driver and BIOS fixes first.

What if I still can’t see the COM port after trying all these steps?

If the port is still missing, the hardware itself may be faulty. Try the device on another PC. If it works there, the issue is with your Windows installation – consider using System Restore to a point before the problem started, or check if a Windows update caused the issue.

Is it safe to manually add a COM port in Device Manager?

Yes, you can add a legacy COM port by going to Action → Add legacy hardware and selecting Ports (COM & LPT). But this only works if the underlying hardware is present; it won’t create a port out of nothing. It’s useful for assigning a specific COM number to a device that’s already detected.

General steps for current mainstream versions; menus can differ by device and version. See the disclaimer or report an error.

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