Stubby is an application that ensures your DNS queries are encrypted between your device and Quad9 by using the DNS over TLS (DoT) protocol.
More information about Stubby can be found on the DNS Privacy Daemon page.
Step 1 - Install
Install the latest version of Stubby for macOS: Stubby GUI for macOS
Depending on your Mac's security settings, you may receive an error when attempting to install Stubby as it is from an "unidentified developer." If you receive this error, select "OK" and then navigate to your System preferences.
Once you are in your System Preferences, navigate to Security & Privacy, ensure you are on the General tab, and then select "Open Anyway" for the StubbyManager.pkg.
You will receive one final prompt to confirm that you want to open "StubbyManager.pkg". Select "Open" and then you should be able to move forward with the traditional macOS installation process.
Step 2a - Manual Configuration
From the StubbyManager homepage, select "Advanced" to configure Stubby to use Quad9's servers.
The "Advanced" button will open a configuration file. To enable the use of Quad9 servers, you will need to remove the comments (#) from before the Quad9's address data and tls_auth_name.
You will also need to comment out the default test servers by adding the # symbol to the front of the lines containing their connection details.
Select "Save" followed by "Apply" to ensure your changes are saved. You are now configured to use Quad9 with Stubby.
Step 2b - Alternate Configuration
MD5 checksum: c73d091a5529bf1c1dce9457dd995898
SHA-1 checksum: 86e588905b293b42cc90a61f1a9220cebeee8235
For more information on configuring Stubby, visit the Configuring Stubby page.