How Do I Change the COM Port for a USB Serial Adapter on Windows?

Last Update: March 3rd, 2026
Article ID: 714099

Originally authored by: Bernie Thompson, July 4, 2011

To change the COM port for a USB Serial adapter on Windows, you must adjust the advanced port settings within the Device Manager. This is often necessary because Windows may automatically assign a high COM port number, while many legacy applications expect a port between COM1 and COM4.

How to Change the COM Port

  1. Open the Device Manager and expand the Ports (COM & LPT)
    Device Manager Ports COM and LPT section
  2. Right-click on your USB Serial adapter device and click on Properties
    Device Manager Ports COM and LPT section context menu
  3. Select the Port Settings tab and click on the Advanced button
    Serial Adapter Properties page
  4. Click on the COM Port Number drop-down menu to change the port to the required port number, ideally between 1 and 4 (some legacy applications expect a COM port in this range)
    Select COM port number from the drop down menu
  5. Click OK on all open Property windows to apply and save the settings. The updated COM port number should now be reflected in the Device Manager
    Verify COM Port number in the Device Manager Port COM and LPT section

Applicable To

PL2303-DB9