PL2303 USB to Serial Adapter on Mac OS 10.13

I have the USB to Serial Adapter PL2303 for which I can’t get a driver working on Mac OS 10.13 (High Siera). I tried two driver versions from the Prolific website: version 2.2.2 and 2.1.0.

I know that the Adapter is fully functional, as it is working with the Serial Application that has it’s own internal drivers. However, I need to be independent of the Serial Application ( ) and therefore install a specific driver on the Mac. When such a driver is loaded, Serial gives a warning that people have reported problems in the past with some adapters and that driver.

Is there any more troubleshooting possible?

Hi Patrick,

Thank you for contacting Plugable! I’m sorry the PL2303-DB9 isn’t working as expected, and I’ll be happy to assist.

The currently recommended driver for PL2303-DB9 in macOS 10.13 High Sierra is version 2.0.0. You can find this driver on the “Downloads” tab of the product page for PL2303-DB9 - here’s a direct download link:

Please note that macOS 10.13 High Sierra features “Gatekeepr” which requires that all third-party extensions are manually approved before they can be loaded by the computer. We have a Knowledge Base article outlining the steps to follow if you come across this issue:

Please let us know how this works out, and feel free to ask if you have any questions.

My apologies for the frustration, and thank you for giving us the chance to help.

Plugable Technologies

Hi Sam.
Thank you for your quick reply.
I installed the version 2.0.0 driver, allowed the changes in Gatekeeper and restarted.
There is not much of a change however. The same warning message when opening Serial and communication with the serial device is not working.

The ProlificUsbSerial.kext seems well installed under /Library/Extensions.
On some Google searches the path is given as /System/Library/Extensions. Should the .kext be in this folder instead?
Here below the entry from the System Report:

USB-Serial Controller:

Product ID: 0x2303
Vendor ID: 0x067b (Prolific Technology, Inc.)
Version: 3.00
Speed: Up to 12 Mb/sec
Manufacturer: Prolific Technology Inc.
Location ID: 0xfd130000 / 4
Current Available (mA): 500
Current Required (mA): 100
Extra Operating Current (mA): 0


Hi Patrick,

I’m sorry to hear the PL2303-DB9 still isn’t working with the 2.0.0 driver.

Regarding the location of the .kext file, the /Library/Extensions folder is the correct location for third-party kernel extensions in modern versions of macOS, including High Sierra. The /System/Library/Extensions folder is used for Apple’s own extensions and should not be modified.

Based on your description of the behavior, our next step is to get some additional information.

Can you please send an email to our direct support email address ( with “For ticket # 430600” in the subject line? In the email, please include the following information:

  1. The Amazon/eBay/Walmart/Newegg order number from your purchase. If it’s from Amazon you can find this at
  2. A set of log files from your system, collected with the PL2303-DB9 connected (even if it is not working as expected). We have a tool that automates this process, which can be downloaded from:
  3. A screenshot ( of the warning message you’re seeing with the PL2303-DB9

This information will help us to determine the next steps.

** Please do not post the above information here in our public forum (it contains personally identifiable information) **

My apologies again for the frustration.

Plugable Technologies

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