Octopus Deploy is built API-first. This means that Octopus is built in layers; all data and operations are available over its REST API. The Octopus Web Portal is built on top of this API so all of the data and operations you can see and perform in the Octopus Web Portal can be performed over the REST API.
Octopus integrates with build servers, scripts, .NET applications, and anything else with its REST API.
The Octopus CLI is the command-line tool that interacts with the REST API and can be used to manage your Octopus Server, infrastructure, and deployments.
Octopus includes a Migration API that provides the ability to back-up and restore parts of an Octopus Deploy instance remotely.