# Versioning

> Dated API versions, what can change within one, and how you hear about changes.

The API has a path version (`/v1`) and a dated version, shown in the `NOWScale-Version` header of every response and in `api_version` on every event. The first dated version is `2026-12-01`.

Within a dated version, changes only add:

- new endpoints and new optional request fields,
- new fields in responses and event payloads,
- new event types (endpoints that listen to all events receive them),
- new error codes and new values in fields documented as open lists.

Write code that ignores fields it does not know and handles an unknown error `code` like a generic error of its status.

A change that could break working code (removing or renaming a field, changing what a value means) comes as a new dated version. Your keys keep their version until you move them, and we announce new versions in the changelog well in advance.