How to Reset a COM Port in Windows for Free: Your Guide to Fix Port Issues

You can reset a COM port in Windows using Device Manager, the Command Prompt, or by reinstalling drivers. Most people solve this in 5 to 10 minutes. Start with Device Manager first—it’s the safest and fastest method for most situations.

Why COM Port Issues Happen

COM ports (serial ports) connect devices like printers, modems, GPS units, and industrial equipment to your computer. When they stop working, it’s usually because:

The driver crashed or became outdated. Windows assigned the port to the wrong device. Too many COM ports are defined in your system. The port got disabled accidentally. Corrupted configuration files prevent the port from starting.

Understanding the cause helps you choose the right fix.

Method 1: Reset COM Port Using Device Manager (Easiest)

Device Manager is the simplest way to reset a COM port. This method works for about 80 percent of COM port problems.

Follow these steps:

1. Press Windows Key + X on your keyboard
2. Click Device Manager from the menu
3. Look for Ports (COM & LPT) in the list
4. Click the arrow next to it to expand the section
5. Right-click the COM port that’s causing problems
6. Select Uninstall device
7. Check the box that says Delete the driver software for this device
8. Click Uninstall
9. Restart your computer

When your computer restarts, Windows will automatically reinstall the COM port driver. This fresh installation usually fixes most issues.

Why this works: You’re telling Windows to forget about the broken configuration and start completely fresh. The driver reinstalls with default, clean settings.

Method 2: Disable and Re-enable the COM Port

Sometimes you don’t need to uninstall. Just turning it off and back on fixes the problem.

Steps to follow:

1. Open Device Manager (Windows Key + X, then Device Manager)
2. Expand Ports (COM & LPT)
3. Right-click the problematic COM port
4. Click Disable device
5. Wait 10 seconds
6. Right-click the same port again
7. Click Enable device
8. Wait for it to finish installing

This is faster than uninstalling and works when the driver itself is fine but the port connection is stuck.

Method 3: Reset COM Port Using Command Prompt

If Device Manager doesn’t work, command-line tools give you more control.

Using Command Prompt:

1. Press Windows Key + R
2. Type cmd
3. Press Ctrl + Shift + Enter to open as Administrator
4. Type this command: mode COM1: baud=9600 parity=n data=8 stop=1
5. Press Enter

Replace COM1 with whichever port you’re fixing (COM2, COM3, etc.).

This command resets the COM port to standard settings. If you need different settings for your device, you can change the values:

baud: 300, 600, 1200, 2400, 4800, 9600, 14400, 19200, 38400, 57600, or 115200. parity: e (even), o (odd), or n (none). data: 5, 6, 7, or 8 bits. stop: 1 or 2 bits.

Using PowerShell for complete reset:

1. Right-click the Start button
2. Select Windows PowerShell (Admin)
3. Copy and paste this command:

Get-PnpDevice -PresentOnly | Where-Object {$_.InstanceId -match ‘COM’} | Disable-PnpDevice -Confirm:$false

4. Press Enter
5. Wait 10 seconds
6. Run this command to re-enable:

Get-PnpDevice -PresentOnly | Where-Object {$_.InstanceId -match ‘COM’} | Enable-PnpDevice -Confirm:$false

This removes and restarts every COM port on your system at once.

Method 4: Remove Conflicting COM Ports

Windows sometimes creates multiple COM port entries that conflict with each other. You might have COM1, COM2, COM3, and others that don’t connect to actual devices.

How to clean this up:

1. Open Device Manager
2. Expand Ports (COM & LPT)
3. Write down which ports are actually connected to devices
4. Right-click any COM port you don’t recognize
5. Select Delete or Uninstall
6. Restart your computer

After restart, Windows only shows ports that are actually there. This often solves conflicts that prevent communication.

Method 5: Update or Reinstall Drivers Manually

If your device came with a driver disc or you downloaded drivers, reinstalling them might help.

Steps:

1. Open Device Manager
2. Right-click the COM port
3. Select Update driver
4. Choose Browse my computer for drivers
5. Navigate to where you saved the driver files
6. Select the folder and click Next
7. Let Windows install the driver
8. Restart your computer

Download the latest drivers from your device manufacturer’s website for the best results. This is especially important for older devices that haven’t been used in years.

Reset Methods

Method	Speed	Difficulty	Best For	Success Rate
Device Manager	Very Fast	Very Easy	General issues	85%
Disable/Enable	Very Fast	Easy	Stuck connections	70%
Command Prompt	Fast	Medium	Advanced control	80%
PowerShell	Fast	Medium	Multiple ports	75%
Driver Update	Medium	Medium	Outdated drivers	90%
Remove Conflicts	Medium	Easy	Multiple COM ports	65%

Common Issues and What To Do

Problem: COM port still doesn’t appear after reset

This usually means Windows doesn’t recognize your device. Try updating the driver manually or check if your device is working properly. Some devices need to be plugged in during driver installation for Windows to detect them.

Problem: Error message about unknown device

Right-click the unknown device and select Update driver. Point Windows to the manufacturer’s website or driver folder.

Problem: Port works briefly, then stops

This often indicates a driver conflict or power management issue. Disable power saving for USB ports in Device Manager. Right-click your COM port, select Properties, go to the Power Management tab, and uncheck Allow the computer to turn off this device to save power.

Problem: Multiple COM ports showing up but only one device connected

These are ghost ports. Use Method 4 to delete the unused ones. This prevents communication problems.

Problem: Getting Access Denied errors in Command Prompt

You need Administrator privileges. Right-click Command Prompt and select Run as administrator before entering commands.

When To Try Something Different

Some COM port problems require different solutions:

Device isn’t being recognized at all: The device itself might be broken. Test it on another computer if possible.

Driver won’t install: The driver might not be compatible with your Windows version. Check the manufacturer’s website for Windows 10 or Windows 11 specific drivers.

Port keeps getting reassigned numbers: Disable and re-enable all USB devices. Sometimes the system reassigns COM port numbers randomly.

Getting hardware errors in Device Manager: Your device cable might be loose or damaged. Reseat all connections and try a different USB port (if applicable).

Prevention: How To Avoid COM Port Problems

Once you fix the issue, prevent it from happening again:

Keep your drivers updated. Check the manufacturer’s website monthly for new versions. Don’t disable unknown devices without checking what they are first. Use the same USB port for the same device repeatedly if possible. Avoid unplugging devices while data is being transferred. Use quality cables that match your device specifications. Install only drivers from the manufacturer, not third-party sites.

Frequently Asked Questions

What is a COM port and why do I need it?

A COM port is a serial communication port that connects devices to your computer. Older printers, GPS devices, industrial equipment, and some specialized hardware use COM ports. Modern devices often use USB instead, but COM ports are still important for legacy equipment and certain applications that require direct serial communication.

Will resetting a COM port delete any of my files?

No. Resetting a COM port only affects the device driver and port configuration. Your files, programs, and personal data remain untouched. You’re only refreshing how Windows communicates with the physical port.

How do I know which COM port number my device is using?

Open Device Manager and expand Ports (COM & LPT). You’ll see the actual device name and its COM number listed there. For example, you might see “USB Serial Port (COM3)”. That means your device is using COM3.

Can I change which COM port number Windows assigns to my device?

Yes. Right-click the COM port in Device Manager, select Properties, go to the Port Settings tab, and click Advanced. You can select a different COM port number from the dropdown menu. However, the default assignment usually works best.

Is it safe to use Command Prompt commands to reset a COM port?

Yes, it’s completely safe. The commands shown here only change configuration settings and don’t affect system files or other devices. Always run Command Prompt as Administrator to ensure the commands work properly.

Summary

Resetting a COM port in Windows is straightforward and free. Start with Device Manager for simplicity. If that doesn’t work, try disabling and re-enabling the port, or use Command Prompt for more detailed control. Removing conflicting COM port entries solves many problems. Most issues resolve within 10 minutes using these methods.

The key steps are:

Open Device Manager and locate your COM port. Uninstall the driver with the option to delete driver files. Restart your computer and let Windows reinstall automatically. Update drivers from the manufacturer if problems persist.

These solutions work without paying for expensive software or calling technical support. Your COM port should function properly after trying these free methods.