---
myst:
  html_meta:
    description: "Defines Ray's API stability guarantees and the PublicAPI (alpha, beta, stable), DeveloperAPI, and Deprecated annotations that label public interfaces. Read this to understand the stability to expect from a Ray API or how to annotate one you're adding."
---

(api-stability)=

# API stability

Ray provides stability guarantees for its public APIs in Ray core and libraries, which are decorated/labeled accordingly.

An API can be labeled:

* {ref}`PublicAPI <public-api-def>`, which means the API is exposed to end users. PublicAPI has three sub-levels (alpha, beta, stable), as described below.
* {ref}`DeveloperAPI <developer-api-def>`, which means the API is explicitly exposed to *advanced* Ray users and library developers.
* {ref}`Deprecated <deprecated-api-def>`, which may be removed in future releases of Ray.

Ray's PublicAPI stability definitions are based on the [Google stability level guidelines](https://google.aip.dev/181), with minor differences:

(api-stability-alpha)=

## Alpha

An *alpha* component undergoes rapid iteration with a known set of users who **must** be tolerant of change. The number of users **should** be a curated, manageable set, such that it is feasible to communicate with all of them individually.

Breaking changes **must** be both allowed and expected in alpha components, and users **must** have no expectation of stability.

(api-stability-beta)=

## Beta

A *beta* component **must** be considered complete and ready to be declared stable, subject to public testing.

Because users of beta components tend to have a lower tolerance of change, beta components **should** be as stable as possible; however, the beta component **must** be permitted to change over time. These changes **should** be minimal but **may** include backwards-incompatible changes to beta components.

Backwards-incompatible changes **must** be made only after a reasonable deprecation period to provide users with an opportunity to migrate their code.

(api-stability-stable)=

## Stable

A *stable* component **must** be fully-supported over the lifetime of the major API version. Because users expect such stability from components marked stable, there **must** be no breaking changes to these components within a major version (excluding extraordinary circumstances).

### Docstrings

```{eval-rst}
.. _public-api-def:

.. autofunction:: ray.util.annotations.PublicAPI

.. _developer-api-def:

.. autofunction:: ray.util.annotations.DeveloperAPI

.. _deprecated-api-def:

.. autofunction:: ray.util.annotations.Deprecated
```

Undecorated functions can be generally assumed to not be part of the Ray public API.