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Deprecate a REST API as a managed migration, not as a header change: define exactly what is affected, identify its consumers, document a supported replacement and migration path, announce a realistic timeline, monitor remaining use, and retire the old interface only according to a clearly stated policy. The key distinction is that Deprecation signals lifecycle status; it does not itself change behavior. Sunset signals that a URI is expected to become unresponsive at a specified time, but does not guarantee a particular shutdown or response.
Deprecation and sunset mean different things
Under RFC 9745, the Deprecation HTTP response header communicates that the resource represented by the response will be or has been deprecated. Its date may be in the future or the past. The signal encourages consumers to migrate and discourages new dependencies, but deprecation alone does not alter the resource’s behavior: it can continue to work as before.
Sunset, defined by RFC 8594, concerns a later lifecycle stage: a URI is expected to become unresponsive at a specified future time. Use it to communicate a planned end of service, not merely that an endpoint or version is no longer preferred. The header is a hint about expected availability; it neither guarantees the resource will be shut down nor specifies what response clients will receive afterward.
| Signal | What it communicates | What it does not do |
|---|---|---|
Deprecation |
The resource in the response context has been or will be deprecated. | It does not change behavior, force a client to migrate, or by itself announce unavailability. |
Sunset |
The URI is expected to become unresponsive at a specified time. | It does not guarantee shutdown or prescribe the post-date status code or response. |
If you send both signals, the Sunset timestamp must not be earlier than the Deprecation date. The RFCs do not establish a universal minimum transition period, so choose dates based on your commitments and consumer needs rather than copying an arbitrary grace period.
Plan the transition before adding headers
1. Define the scope precisely
Decide whether you are deprecating one endpoint, a group of resources, a feature, or an entire API version. The header in an individual response concerns the resource in that response context. If your policy applies to a broader surface, spell out that scope in the API documentation and communications; a client should not have to guess whether one header applies to neighboring endpoints.
2. Identify consumers and establish a baseline
Use available request logs, account-level analytics, or other production usage data to determine who calls the affected surface and how frequently. Record a baseline before the announcement so you can assess migration progress. Where possible, distinguish clients by account, credential, or other reliable identifier, while respecting your privacy and contractual obligations.
Not every provider can identify every downstream user. A consumer may proxy requests or share credentials, and some traffic may not map cleanly to a responsible team. Record those limits instead of treating unknown traffic as migrated.
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Name the supported replacement endpoint or version and publish concrete migration material before asking clients to move. Include the breaking changes, request and response examples, any new authentication or permissions requirements, and differences in errors, pagination, rate limits, or data semantics where applicable. Link to a migration guide from the response where practical, and keep the guide available throughout the transition.
When the replacement requires behavior changes rather than a path substitution, explain what clients must change and test. A nominally similar endpoint is not a safe replacement if it returns different data or has different operational constraints.
4. Set and communicate dates
Choose a deprecation date and, if you have decided to retire the resource, a separate expected sunset date. Check support commitments, contracts, and applicable obligations before publishing dates. Make the schedule visible in your API documentation and changelog; notify affected consumers through channels they are likely to receive, such as account communications, email, dashboards, or support contacts.
Runtime headers can inform software and developers inspecting responses, but they do not ensure that a human service owner sees the notice. The HTTP standards do not prescribe a notification channel or a universal grace period.
5. Monitor migration and help remaining consumers
Continue measuring requests to the old resource through the transition. Compare usage to your baseline, investigate persistent callers, and contact affected consumers where you can. Usage monitoring during the sunset phase is also recommended by Zalando’s RESTful API guidelines to observe migration progress and reduce uncontrolled breaking effects.
Do not assume a client has migrated because it accepts, ignores, or fails to display a deprecation header. Verify traffic against the old interface and, where feasible, validate that consumers have moved to the intended replacement.
6. Retire according to the published policy
At the announced date, implement the behavior you documented, and ensure operational staff can recognize requests to the retired surface. Decide in advance whether callers receive an error, a redirect, or another response; consider whether preserving a limited compatibility path is necessary. RFC 8594 does not prescribe the result after the sunset date, so make the actual policy explicit rather than implying that the header defines it.
Return the signals in HTTP responses
For a response to an affected resource, send the applicable Deprecation value and a Link to useful deprecation or migration information. If retirement is planned and the expected-unresponsive date is settled, you may also send Sunset. RFC 9745 describes links to human-readable documentation, replacement information, and information about when the resource becomes non-operational.
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HTTP/1.1 200 OK
Content-Type: application/json
Deprecation: @1688169599
Sunset: Thu, 31 Dec 2026 23:59:59 GMT
Link: <https://api.example.com/docs/migrations/v1>; rel="deprecation"This is a syntax illustration, not a recommended schedule or a ready-to-copy date. Confirm both timestamps, the date formats, the affected resource scope, and the linked documentation before deploying. Omit Sunset until you have an actual expected retirement date; do not use it just to label a resource as discouraged.
RFC 9745 also describes using Link information for a replacement. If you publish a replacement link, make sure it identifies the replacement clearly and resolves to documentation or a resource consumers can actually use. Keep the migration page accessible for the lifetime of the transition.
Choose a rollout policy for your consumers
There is no standards-mandated deprecation interval. Compare the following factors when setting the dates and deciding how to support the transition:
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- Scope: a single resource is usually easier to assess than a whole API version with many endpoints.
- Consumer impact: consider the number and importance of known integrations and the cost of changing them.
- Migration complexity: a compatible replacement may be straightforward; a redesign that requires retesting needs more planning.
- Observability: assess whether you can identify callers and distinguish old-interface use from successful migration.
- Commitments: review your published support policy, agreements, and applicable legal or regulatory obligations. The appropriate requirements depend on the provider, jurisdiction, and agreement.
- After-date behavior: decide what the server will actually do and make that behavior supportable and understandable to clients.
What a version-wide transition can look like
GitHub’s REST API versioning guidance is one provider-specific example of connecting version selection, migration information, runtime signals, and retirement behavior. Clients specify a version using X-GitHub-Api-Version; GitHub advises consumers to review breaking-change changelogs and make the changes required by a newer version. Its documentation describes Deprecation and Sunset response headers as migration signals and states that requests specifying a version after its support window ends receive 410 Gone. Those details illustrate one implementation, not a universal timetable or required status code.
For your own API, put version selection and breaking-change documentation in the same migration plan as response headers. State what happens to requests after retirement instead of assuming consumers will infer it from another provider’s policy.
Troubleshoot common rollout problems
Clients see no deprecation signal
Confirm the affected route actually emits the header on the response clients receive, including responses served by gateways, caches, or proxies. Verify that the header is not limited to one code path while other representations of the same resource omit it. Ensure API documentation explains the intended scope.
A date is rejected or displayed incorrectly
Check the syntax for the specific field: Deprecation uses an HTTP Structured Field Date; Sunset uses an HTTP-date. Validate that the date is parseable and that, when both are present, the sunset timestamp is not earlier than the deprecation date.
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A header is not a migration guide. Link to documentation that names the replacement and describes breaking changes with examples. Also use the communication channels established for your consumers, since automated clients may record a header without bringing it to an owner’s attention.
Old-version traffic remains near the retirement date
Recheck account-level usage and your consumer mapping, then contact known owners and investigate whether the replacement is blocked by missing functionality or an incomplete migration path. Do not treat a calendar date or a falling aggregate request count as proof that all important clients have moved.
Clients expect a particular response after sunset
Clarify the retirement behavior in your docs and update the operational plan. The Sunset field is not a promise of 410 Gone or any other specific result; choose and communicate that behavior yourself.
Automate related web-page captures when documenting a migration
If your team needs current screenshots of API documentation pages for an internal migration guide, support handoff, or release review, capture the pages you need and retain the URL and capture context alongside them. Avoid treating a screenshot as a substitute for versioned API documentation or a machine-readable changelog.
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With Playwright for Node.js, install the package with npm install playwright and install a browser with npx playwright install chromium. Save this as capture-docs.mjs, replacing the example URL and output filename as needed:
import { chromium } from 'playwright';
const browser = await chromium.launch({ headless: true });
try {
const page = await browser.newPage({ viewport: { width: 1440, height: 1000 } });
await page.goto('https://api.example.com/docs/migrations/v1', {
waitUntil: 'networkidle',
timeout: 60000
});
await page.screenshot({ path: 'migration-guide.png', fullPage: true });
} finally {
await browser.close();
}Run it with node capture-docs.mjs. It writes a full-page PNG after navigation reaches network idle. A page with long-lived network requests may never reach that state; in that case, wait for a relevant selector or use a bounded delay suited to the page, rather than removing timeouts entirely. Authenticated or restricted docs may require a browser context with the appropriate session, and client-side content may need an explicit ready-state check.
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ScreenshotNeo can return a website screenshot or PDF with one GET request. Its clean-shot options accept cookie or consent banners like a visitor and remove 60+ known consent platforms, newsletter popups, and chat widgets; each step can be turned off. Bot checks or CAPTCHAs, blank pages, timeouts, failed loads, and cache hits are not billed, with response headers indicating page verdict and billing status. Its MCP server offers take_screenshot, get_page_info, and capture_pdf for Claude, Cursor, and other MCP clients. The free plan includes 1,000 shots per month with no card; paid plans start at $5 for 3,000 shots.
curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://api.example.com/docs/migrations/v1 -o migration-guide.webpSee the ScreenshotNeo API documentation for request options and response details. Sign up for 1,000 free screenshots a month with no card.
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Frequently asked questions
Can a provider deprecate a resource without setting a sunset date?
Yes. Deprecation communicates lifecycle status; a sunset date is relevant when the provider expects the URI to become unresponsive and has selected a date to communicate.
Do the RFCs prescribe how long consumers must have to migrate?
No. RFC 9745 and RFC 8594 define signals, not a universal transition duration. The timeline depends on the provider’s commitments and the practical needs of affected consumers.
Does receiving a deprecation header mean a client must stop using the endpoint immediately?
No. The header communicates that the resource is or will be deprecated. The provider’s documentation should explain the replacement and schedule; the header alone does not change resource behavior.
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