This demo shows how the end to end process of connecting BuiltWith to Salesforce and adding a custom field to sync. Get Started Here....
This step by step guide provides instructions on how to configure your Salesforce installation to allow BuiltWith to push results to it using the Lighting Experience....
Salesforce
Open the Connect App settings screen and turn off "Require Proof Key for Code Exchange (PKCE) Extension for Supported Authorization Flows" ....