# Extending Flows with Apps

Spacelift Flows offers a very small number of built-in blocks. Instead, it exposes a set of core services that can be used by [Apps](../../apps) to implement higher level functionalities.

In this section, you’ll find documentation on how to [build your own Apps](./building-apps/) and blocks using these services, [use them internally](./deploying-apps/custom-apps), and expose them to external users via [registries](./deploying-apps/app-registries).