> ## Documentation Index
> Fetch the complete documentation index at: https://developers.luccasoftware.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Introduction

> Earlier versions of the Lucca APIs, still available during the transition to the Lucca API.

<Note>
  The **[Lucca API](/api-reference/latest/introduction)** is our current public API. It offers a stable, versioned contract with
  OAuth 2.0 authentication and long-term support guarantees.

  If you are starting a new integration, we recommend using the Lucca API directly.
</Note>

The previous APIs documented in this section predate the Lucca API. They were originally designed for
internal use and made available publicly over time. As such, they differ from the Lucca API in a few ways:

* They follow [different conventions](./api-generations) depending on when they were introduced.
* They are not versioned — changes may be applied without a formal deprecation cycle, but we will still notify you in advance whenever possible.
  Make sure a valid contact email is associated with your API keys so you can be notified ahead of time.
* They do not use a modern authentication scheme (API keys rather than OAuth 2.0).

These endpoints are **production-ready** and actively used by thousands of customers every day.
You can safely build integrations on them. As the Lucca API expands its coverage, equivalent
endpoints will become available and migration guides will be provided.

<Card title="Download the OpenAPI specifications" icon="file-arrow-down" arrow="true" href="./download">
  Download the OpenAPI specifications of the Lucca Legacy APIs to generate client libraries, create API documentation, and more.
</Card>