How to change the COM port for a USB Serial adapter on Windows 7

Start by going to the Device Manager. Once there do the following:
Expand the Ports ‘(COM& LPT)’

You should be looking at something like this:

As you can see Windows has set the port to COM10. However many legacy applications expect the port to be between 1-4. Let’s change that:
Right click on the device and click on ‘Properties’.

Click on ‘Port Settings’. Then click on ‘Advanced…’.

Once you’re in ‘Advanced Settings for COM10’ on the bottom you can see the ‘COM Port Number: COM10’. Click on that to change it to the lowest possible number (between 1-4).

Then click ‘OK’ on all open Property Windows.
Now the device should look like this:

31 comments on “How to change the COM port for a USB Serial adapter on Windows 7”

  1. Philmore Sydney Reply

    Just what to say thanks. This website has been very useful in assisting me in getting my usb to serial adapter to work. On my computer however there are no serial ports but when I follow the steps as above to change the com port when the usb to serial is plugged in quite a few of the ports in the drop down list has the status ‘in use’ next to them. Can you tell me the reason for this?


      • laserman Reply

        I found a code that allows you to remove old associations to COM Ports. You can then plug your adapter in and then associate it with the COM Port you need.

        1. Start, All Programs, Accessories, Right-click “Command Prompt” in Accessories and choose “Run as Administrator”
        2. Enter “set devmgr_show_nonpresent_devices=1″ – without the quotes obviously
        3. Enter “start devmgmt.msc”
        4. In the box that opens, select “Show hidden devices” in the ‘view’ menu.

        Now if you expand the section on COM ports, all the COM ports that have ever
        been created will be displayed, the non present ones being in grey. You can
        uninstall away anything that you don’t want (right click, select uninstall).

  2. Canton Reply

    Thanks a lot for the helpful article. If you don’t mind though, I’d appreciate you’re help, as I’m a bit stuck. When I go to the “properties” dialog for my USB to Serial Port, there is no tab for “port settings.” The tab does appear in the properties dialog of other COM ports though, just not the USB to Serial port. I’ve tried updating the driver, to no avail.

    Any help would be much appreciated!

    • Bernie Thompson Bernie Thompson Reply

      Hi Canton – Can you say what brand of adapter (and if not Plugable, what chipset / driver), and what OS you’re on. Thanks!

  3. matt Reply

    There is no tab for port settings in windows 7 home. Do u know how to change port settings in windows 7 home?

    • Jeff Everett Jeff Everett Reply

      Hi Matt-

      Sorry to hear you’re not seeing the port settings tab, and the delay in getting back to you.

      Our screenshots for this article were done on Windows 7 Home, and the user interface is the exact same on Pro and Ultimate just for the record.

      We’re happy to help if you’re still stuck on this and want to provide a little more info: are you seeing the “Prolific USB-Serial Comm Port” device under device manager, or something else?

      Jeff Everett
      MCITP Enterprise Support Tech

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  5. ray Reply

    I also have the problem where the Prolific USB to serial is installed on com11 and the “advanced” button leads to anohter screen, but there is no provision for changing com port there. Might be IT department blocks that on company PC. I blame the device driver installation software -it SHOULD show defaults and ASK the user if they want to make changes before installing. No nothings can just push the button to install defaults, those of use who know what settings we need could then get it right.

  6. Brad Fluharty Reply

    I just received my Plugable USB to RS-232 DB9 Serial Adapter, and after downloading and installing the updated drivers and tweaking the Com port, was able to use my Icom PCR-1000 for the first time in 6 or 7 years. Receiver software still telling my that it cannot find the port, but it seems to be fully functional. Brad

  7. Steve Reply

    Is there any way to make sure that Windows 7 does NOT swap the port setting once they are set using the above method?

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  9. Ganesha.B.S Reply

    How can I open the port in windows 7 and send commands to that port also get acknowledgement?

  10. Gellan Reply

    thank you so much. I wanted to change the port number of my arduino, but couldn’t find a way to do so. this is the one and only method which worked for me. thanks again for sharing.

  11. Gerry Reply

    none of that worked for me . I am trying to down load a game & it keeps giving me errors when I try to change the port there is nothing there.

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