How to Write an API Versioning Announcement in English
Learn how to announce a new API version in English — explaining what's new, the deprecation timeline for the old version, and clear migration steps for integrating developers.
Announcing a new major API version is different from announcing a feature release — it usually means an old version will eventually stop being supported, and every integrated developer needs to decide when and how to migrate. The English in this kind of announcement needs to be unambiguous about what’s changing, what’s staying the same, and exactly how much time developers have. This guide covers how to write it.
Key Vocabulary
Major version — a version that includes breaking changes, requiring integrating developers to update their code, as opposed to a minor version that’s backward compatible. “v3 is a major version — it includes breaking changes to the authentication flow, so this isn’t a drop-in upgrade from v2.”
Breaking change — a change that will cause existing integrations to fail or behave incorrectly if they aren’t updated.
“The breaking change here is that the status field now returns a string enum instead of a numeric code — any code parsing it as a number will break.”
Sunset date — the date after which an old version stops working entirely, as distinct from a deprecation date, which just marks the start of the warning period. “v1 is deprecated as of today and will be fully sunset on [date] — after that date, requests to v1 endpoints will return an error.”
Parallel support window — the period during which both the old and new versions are simultaneously available, giving developers time to migrate at their own pace. “We’re maintaining a six-month parallel support window where both v2 and v3 are fully functional, so you can migrate on your own timeline within that window.”
Migration guide — a document mapping old behaviour to new behaviour field by field or endpoint by endpoint, so developers can update their integration systematically. “Our migration guide includes a side-by-side comparison of every changed endpoint, with example requests and responses for both versions.”
Structuring the Announcement
- What’s new: “API v3 introduces cursor-based pagination, a unified error response format, and OAuth 2.1 support across all endpoints.”
- What’s changing for existing integrations: “If you’re on v2, note that the
pageandlimitquery parameters are replaced bycursorandpageSizein v3.” - Timeline: “v2 is not being deprecated immediately — it will remain fully supported until [date], giving you a six-month window to migrate.”
- How to migrate: “Our migration guide at [link] walks through every breaking change with before/after examples. We also provide a compatibility-checking script you can run against your integration.”
- Support during migration: “If you hit any issues migrating, our developer support team is available at [contact] specifically for v2-to-v3 migration questions.”
Explaining the Reasoning
- “We moved to cursor-based pagination because offset-based pagination was causing performance problems and inconsistent results on large datasets — this fixes both.”
- “The unified error format means every endpoint now returns errors in the same shape, which should simplify your error-handling code significantly once migrated.”
- “We know major version changes are disruptive, which is why we’re giving a full six months of parallel support rather than a shorter window.”
Handling Developer Questions
- “Yes, v2 will continue to work exactly as it does today until the sunset date — there’s no rush, but we do recommend starting the migration sooner rather than closer to the deadline.”
- “For most integrations, the pagination change is the only breaking change you’ll encounter — the migration guide’s ‘Quick Wins’ section covers that specific update first.”
- “If six months isn’t enough time for your specific integration, reach out to us directly — we can discuss an extended timeline for complex migrations.”
Professional Tips
- Separate “what’s new” from “what breaks.” Developers scanning the announcement need to immediately find the section that tells them whether their code needs to change.
- Always give a parallel support window, not a hard cutover. A generous overlap period is the single biggest factor in how smoothly a version migration goes for your ecosystem.
- Provide a migration guide, not just a changelog. A changelog tells developers what changed; a migration guide tells them exactly what to do about it.
Practice Exercise
- Write a two-sentence summary announcing a new major API version, including the parallel support window length.
- Draft one paragraph explaining a specific breaking change (your choice) and how to update code to handle it.
- Write a response to a developer asking whether their existing v2 integration will break immediately after the announcement.