# SingleFax API versioning and deprecation

The public REST API is versioned in the URL path: `/api/v1` on https://singlefax.com and https://api.singlefax.com. OpenAPI is `/openapi.json` (`info.version` 1.0.0). There is no sunset scheduled.

## Versioning

Additive, backward-compatible changes stay on v1. Breaking changes ship as `/api/v2`. We do not silently change v1 request or response shapes.

## Deprecation and Sunset

When a v1 operation or field is going away, responses include RFC 8594 `Deprecation` and `Sunset` (at least 90 days later). OpenAPI marks the same operations `deprecated: true`. MCP tools at `/mcp` use the same notice window.

No v1 operation currently carries Deprecation or Sunset.

HTML: https://singlefax.com/versioning
OpenAPI: https://singlefax.com/openapi.json