If you've run into a problem where you have some audio plug-ins that are not working on Catalina after copying them over to the respective folder (e.g. vst/, vst3/, component/, etc), then you can run the following commands in the terminal to allow your DAW to read the plug-in.

The following content is taken from a Reddit comment on this post.

How to remove "unidentified developer" warning

The biggest culprit of plugins by "unidentified developer" is Apple's quarantine flag that prevents the execution of plugins in DAWs. Here is what I typically do:

  • download example.vst plugin file or unpack it from package installer
  • open terminal
  • copy the .vst into /Library/Audio/Plugins/VST (requires admin password)sudo cp ~/Downloads/example.vst /Library/Audio/Plugins/VST
  • navigate to /Library/Audio/Plugins/VSTcd /Library/Audio/Plugins/VST
  • check for extended attributesxattr -lr example.vst
  • delete quarantine and mac ACL attributes and any other attributes the plugin may havesudo xattr -rd com.apple.quarantine example.vstsudo xattr -rd com.apple.macl example.vst

To double-check your work, when in /Library/Audio/Plugins/VST directory the following command should produce no output

  • xattr -lr com.apple.quarantine example.vst

Restart your DAW and rescan for plugins and you should see your new plugin. If not then go ahead with restarting your mac, sometimes they don't appear before system restarts.

The same process applies to AU and VST3 plugin formats just with respective paths.

Why does this happen?

Gatekeeper is a security feature of the macOS operating system by Apple. It enforces code signing and verifies downloaded applications before allowing them to run, thereby reducing the likelihood of inadvertently executing malware.

If the creator of the plug-in has not registered with Apple as a developer the warning will be enabled by default.