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RFC 8594 / START HERE

Sunset, before the details

HTTP means Hypertext Transfer Protocol. Sunset is the name of a response field, not an acronym. It supplies a possible retirement time for the resource identified by a URI.

RFC 8594 defines a Sunset date hint and the sunset link relation for finding policy or migration information. Neither guarantees an exact shutdown or automatically moves a client.

Start the guide See the 4 chapters ↓

The idea in one picture

  1. A resource advertises intent

  2. Inspect timing and policy

  3. Plan without assuming a guarantee

A simplified picture of the idea; the chapters explain the actual mechanisms.

Why it exists

Services can know in advance that temporary resources or API versions may stop responding. Early information can help users plan, while keeping normal caching and uncertainty about future availability separate.

A familiar example

A fictional API announces Wed, 11 Nov 2026 11:11:11 GMT and links to its retirement policy. A client can prepare, but must still check actual availability and assess any migration advice before acting.

Helpful background

You can start here without reading another RFC. If these ideas are unfamiliar, these short introductions may help.

HTTPRFC 9110 · beginner overview ↗CachingRFC 9111 · beginner overview ↗

What you’ll learn next

Begin with chapter one, or choose a topic.

  1. Read a retirement hint, not a guaranteeA Sunset response field advertises when a resource is expected to become unresponsive; it does not guarantee availability on either side of that date.
  2. Keep caching and retirement separateCache policy governs reuse of a representation; Sunset describes expected resource availability and says nothing about intervening state changes.
  3. Distinguish resource scope from service policyThe default hint concerns the responding resource. Broader service scope exists only through additional rules that a client understands.
  4. Follow policy information without blind migrationA sunset link can explain policy, timing or migration options. It does not redirect the client or authorize automatic identity changes.
Start with chapter one →

This introduction explains RFC 8594 (2019). Read the original RFC ↗