Sunset Header website screenshot

Sunset Header

The Sunset HTTP header field (RFC 8594) is an informational IETF specification that allows servers to communicate to clients that a URI is likely to become unresponsive at a specified future point in time. Published in May 2019, it provides a standardized mechanism for API deprecation signaling, enabling clients to plan migrations before service retirement. The header value is an HTTP-date timestamp following RFC 7231 syntax. A complementary sunset link relation type allows resources to reference documentation covering the sunset policy, migration guidance, and alternatives. RFC 9745 (Deprecation HTTP Header Field) extends this pattern by providing a two-phase deprecation + sunset lifecycle where Deprecation marks the start of deprecation and Sunset marks the end-of-life. These two headers are widely adopted in REST API governance practices and API lifecycle management tooling.

Sunset Header publishes 2 APIs on the APIs.io network. Tagged areas include API Deprecation, HTTP Headers, RFC 8594, RFC 9745, and API Lifecycle.

The Sunset Header catalog on APIs.io includes 1 JSON-LD context and 1 Spectral governance ruleset.

🌐 Visit website 📡 Source on GitHub
14.0/100 emerging ▬ flat Agent 3/100 human only Full breakdown ↓
scored 2026-08-25 · rubric v0.14.0
AccessFreemium
2 APIs
API DeprecationHTTP HeadersRFC 8594RFC 9745API LifecycleREST APIsStandards

Kin Score

Kin Score Kin Score How this is scored →
scored 2026-08-25 · rubric v0.14.0
Composite quality — 14.0/100 · emerging
Contract Quality 2.7 / 25
Developer Ergonomics 0.0 / 20
Access Clarity 3.2 / 20
Operational Transparency 1.0 / 13
Contract Governance 1.2 / 12
Discoverability 5.9 / 10
Agent readiness — 3/100 · human only
Machine-Readable Contract 0 / 18
Agentic Access Contract 0 / 10
Documented Reversibility 0 / 6
MCP Server 0 / 12
Machine-Readable Auth 0 / 10
Idempotency 0 / 9
Stable Error Semantics 0 / 8
Request/Response Examples 0 / 7
Rate-Limit Signaling 7 / 7
Typed Event Surface 0 / 6
Agent Skills 0 / 5
Well-Known Catalog 0 / 4
Consent & Bot Identity 0 / 3
A2A Agent Card 0 / 8
Dry-Run / Simulate Mode 0 / 4
Delegated User Identity 0 / 6
Protected Resource Metadata 0 / 5
Registration Without a Human 0 / 6
Agentic Commerce Surface 0 / 5
Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. This rating is computed from github.com/api-evangelist/sunset-header: open an issue to ask a question, or submit a pull request to add artifacts. Want it done for you? Prioritized profiling — $2,500 →

APIs 2

Individual APIs this provider publishes, each with its own machine-readable definition.

Sunset Header (RFC 8594)

The Sunset HTTP header field (RFC 8594) communicates the deprecation timeline of API endpoints to consumers. The header value is an HTTP-date timestamp indicating when a URI is ...

Deprecation HTTP Header Field (RFC 9745)

RFC 9745 defines the Deprecation HTTP response header field, which signals to clients that a resource has been or will be deprecated. It complements the Sunset header by marking...

Pricing Plans 1

Published pricing tiers and plan structures.

Sunset Header Plans Pricing

3 plans

PLANS

Rate Limits 1

Documented rate limits and quota policies.

Sunset Header Rate Limits

5 limits

RATE LIMITS

FinOps 1

Cost, billing, and metering signals for API financial operations.

Sunset Header Finops

FINOPS

Semantic Vocabularies 1

JSON-LD contexts and semantic vocabularies used across these APIs.

Sunset Header Context

0 classes · 15 properties

JSON-LD

Spectral Rules 1

Spectral governance rulesets for linting and validating these APIs.

Sunset Header API Rules

5 rules · 3 warnings 2 info

SPECTRAL

JSON Schema 1

Standalone JSON Schema definitions for this provider's data models.

Sunset Header

9 properties

JSON SCHEMA

Examples 1

Example request and response payloads for these APIs.

Sunset Header Response Example

6 fields

EXAMPLE

Security Posture 1

Authentication, domain security, vulnerability disclosure, and trust-center signals.

Sunset Header Domain Security

TLSv1.3 · HSTS · DNSSEC · DMARC

SECURITY

Resources

Documentation 1

Reference material describing how the API behaves

IETF Specification
IETF Specification

Access & Security 1

Authentication, authorization, and security posture

DomainSecurity
DomainSecurity

Company 1

The organization behind the API

Website
Website

Source (apis.yml)

apis.yml Raw ↑ 
aid: sunset-header
name: Sunset Header
description: The Sunset HTTP header field (RFC 8594) is an informational IETF specification that allows servers to communicate
  to clients that a URI is likely to become unresponsive at a specified future point in time. Published in May 2019, it provides
  a standardized mechanism for API deprecation signaling, enabling clients to plan migrations before service retirement. The
  header value is an HTTP-date timestamp following RFC 7231 syntax. A complementary sunset link relation type allows resources
  to reference documentation covering the sunset policy, migration guidance, and alternatives. RFC 9745 (Deprecation HTTP
  Header Field) extends this pattern by providing a two-phase deprecation + sunset lifecycle where Deprecation marks the start
  of deprecation and Sunset marks the end-of-life. These two headers are widely adopted in REST API governance practices and
  API lifecycle management tooling.
type: Index
accessModel:
  pricing: freemium
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Freemium
  confidence: medium
  source:
  - plans
  generated: '2026-07-22'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/sunset-header.png
tags:
- API Deprecation
- HTTP Headers
- RFC 8594
- RFC 9745
- API Lifecycle
- REST APIs
- Standards
url: https://raw.githubusercontent.com/api-evangelist/sunset-header/refs/heads/main/apis.yml
created: '2026-03-29'
modified: '2026-05-02'
specificationVersion: '0.23'
apis:
- aid: sunset-header:sunset-header
  name: Sunset Header (RFC 8594)
  description: The Sunset HTTP header field (RFC 8594) communicates the deprecation timeline of API endpoints to consumers.
    The header value is an HTTP-date timestamp indicating when a URI is expected to become unresponsive. It is accompanied
    by a sunset link relation type for linking to deprecation documentation and migration guidance.
  humanURL: https://datatracker.ietf.org/doc/html/rfc8594
  tags:
  - HTTP Headers
  - API Deprecation
  - RFC 8594
  - Sunset
  - API Lifecycle
  properties:
  - type: Documentation
    url: https://datatracker.ietf.org/doc/html/rfc8594
  - type: Specification
    url: https://www.rfc-editor.org/rfc/rfc8594
- aid: sunset-header:deprecation-header
  name: Deprecation HTTP Header Field (RFC 9745)
  description: RFC 9745 defines the Deprecation HTTP response header field, which signals to clients that a resource has been
    or will be deprecated. It complements the Sunset header by marking the start of the deprecation lifecycle. The header
    value is a structured date (Unix timestamp per RFC 9651). The Sunset timestamp, if present, must not be earlier than the
    Deprecation timestamp.
  humanURL: https://www.rfc-editor.org/rfc/rfc9745.html
  tags:
  - HTTP Headers
  - API Deprecation
  - RFC 9745
  - Deprecation
  - API Lifecycle
  properties:
  - type: Documentation
    url: https://www.rfc-editor.org/rfc/rfc9745.html
  - type: Specification
    url: https://datatracker.ietf.org/doc/html/rfc9745
common:
- type: DomainSecurity
  url: security/sunset-header-domain-security.yml
- type: Website
  url: https://datatracker.ietf.org/doc/html/rfc8594
- type: IETF Specification
  url: https://www.rfc-editor.org/rfc/rfc8594
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com

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