Big Sur Troubleshooting Guide

Version 2021.03.18

The Big Sur update introduces a number of major changes in macOS. One of them is disabling of the Network Kernel Extensions (NKE) API, which Proxifier for Mac v2 uses. The new Network Extensions API has been introduced to replace it. We have rewritten the network part of Proxifier to adapt to this change. Together with other improvements, Proxifier for Mac v3 has been released.

Proxifier License Upgrade

Proxifier for Mac v3 requires a new license. Upgrade options depend on the date of your v2 purchase.
If you purchased Proxifier for Mac v2 on or after:

You can extract your current v2 key using one of the following commands in Terminal:

Configuration Migration

Proxifier for Mac v3 includes the File->Import v2 Profile... menu command, which allows you to import configuration from v2. Alternatively, you can save profile to a file using File->Export... in v2 and then import the file using File->Import... in v3.

Because Proxifier for Mac v3 runs in a sandbox, it is technically impossible for it to migrate the profiles automatically.

Technical Issues

Unfortunately, the new Big Sur API is currently unstable. There are issues that persist when Proxifier is running even with an empty configuration, and they do not depend on Proxifier configuration or code. These issues have been reported to Apple, and we hope they will be resolved in future Big Sur updates.

Please feel free to contact us at We will do our best to help you.

Special Build to Address Big Sur Problems

To mitigate the problems, we have prepared a special build of Proxifier for Mac v2 that supports Big Sur using private API.

If you have problems with Proxifier for Mac v3, you can use this build. You can also try workarounds for some known issues, which are listed below.

Kernel Panic

Some systems may experience unexpected crashes when Proxifier is working. Kernel Panic log may contain a message like "a freed zone element has been modified in zone flow_divert_pcb".


This is a known problem in Network Extension API. Apple is working on it (FB8901130).

Fail to Connect with Mobile Devices

Applications such as FaceTime or Sidecar may fail to connect macOS with mobile devices like iPhone or iPad.


This is a known problem in Network Extension API. It has been reported to Apple (FB9002173).

Applications Cannot Bind a Port for Listening

Applications report errors such as "Protocol wrong type for socket", "Failed to find a free local port", and "Protocol wrong type for socket (Listen failed)".


There is a bug in Network Extension API in the current version of macOS Big Sur. Apple has been aware of it since September. Hopefully, the problem will be fixed in the next Big Sur update.

Cisco IPSec does not work

Cisco IPSec does not work when Proxifier is running.


This is a known bug in macOS Big Sur.