# API Sunset and Deprecation Headers
Status: public
Confidence: medium (0.865) (verified)
Last verified: 2026-06-02
Generation: ai_structured


## TL;DR

Sunset and Deprecation headers give API clients and agents machine-readable warnings before an endpoint is removed.

## Core Explanation

Deprecation is a lifecycle signal, not just a changelog sentence. HTTP response headers can tell clients that an endpoint is deprecated, when it may stop working, and where to find related migration links.

Agents should use these headers as evidence for migration planning. They should still check documentation, client usage, and version policy before recommending endpoint removal or automated SDK updates.

## Source-Mapped Facts

- RFC 8594 defines the Sunset HTTP response header field for indicating when a URI is expected to become unresponsive. ([source](https://datatracker.ietf.org/doc/html/rfc8594))
- RFC 9745 defines the Deprecation HTTP response header field for communicating deprecation. ([source](https://datatracker.ietf.org/doc/html/rfc9745))
- RFC 8288 defines Web Linking for expressing typed links in HTTP header fields. ([source](https://datatracker.ietf.org/doc/html/rfc8288))

## Further Reading

- [RFC 8594 Sunset Header](https://datatracker.ietf.org/doc/html/rfc8594)
- [RFC 9745 Deprecation Header](https://datatracker.ietf.org/doc/html/rfc9745)
- [RFC 8288 Web Linking](https://datatracker.ietf.org/doc/html/rfc8288)