Groundhogg provides a REST API that allows users to retrieve data remotely using a JSON format. Using the RESTful API users can manage contacts, emails, SMS and tags remotely.
By default, Groundhogg enables its REST API. If you want to disable it you can do that from Groundhogg->Settings->API page.
Groundhogg registers different endpoints that you can use to communicate with the platform.
Here you can see a new namespace is added which is "gh/v3/". The Groundhogg API provides direct access to admin methods thus, authentication is an inevitable part of using the API.