# Versioning

[Open in the interactive reference](https://docs.api.lensing.ai/?op=guide%3Aversioning)

Every request names the version it is written against in the `Api-Version` header. A request without the header, or with a version that does not exist, is refused with `400`. Because the version is always explicit, an integration keeps the contract it was built against.

An endpoint that is not part of the requested version answers `404`, exactly like a path that does not exist.

## Examples

**Pinning a version**

```
Api-Version: v1
```