HubSpot is retiring every legacy semantic-versioned API (v1, v2, v3, and v4) in September 2027, replacing them with date-based versions in a /YYYY-MM/ format such as /2026-09/. v4 APIs and the /2025-09/ CRM APIs lose support earlier, at the /2027-03/ release in March 2027. Portals with affected apps are already receiving "Apps with API versions to update" notifications, and a built-in audit tool at Development → Migrations → APIs lists every legacy endpoint your integrations call. This guide is for HubSpot admins, RevOps and Marketing Ops leads, and business owners — not just developers — and covers what changed, how to check your portal, and the migration steps to schedule now. All dates and steps come from HubSpot's own documentation, linked under Sources, as of October 2026.
/2026-09/, released each March and September, immutable, with a minimum 18-month support window./2025-09/ CRM APIs sunset at the /2027-03/ release (March 2027); all remaining legacy APIs sunset in September 2027./crm/v3/objects/contacts becomes /crm/objects/2026-09/contacts — but request bodies and response shapes can differ, so check field by field.If you admin a HubSpot portal, this notice may already be waiting for you. HubSpot is surfacing "Apps with API versions to update" notifications in accounts where installed apps still call legacy endpoints — and the list it generates is the starting point for a migration every HubSpot customer with integrations needs to complete before September 2027.
The good news: HubSpot has given unusually long lead time, the audit tooling is built into the product, and for many integrations the fix is closer to a find-and-replace than a rebuild. The risk is ignoring it because it looks like a developer problem. It is not — it is an operations problem with a developer task at the end.
On March 30, 2026, HubSpot announced the move from semantic API versions (v1, v2, v3, v4) to date-based versions in a /YYYY-MM/ format, such as /2026-03/ and /2026-09/ (read the changelog announcement). Under the new model, described in HubSpot's platform versioning documentation:
/2026-09/ ships, its behavior does not change under you.For teams that maintain integrations, this is a genuinely better model: the version in your URL tells you its age and its support horizon at a glance. HubSpot's developer's guide to date-based versioning walks through the reasoning in detail. But the same change sets the clock on everything built before it.
Per HubSpot's legacy API migration guide (last modified September 15, 2026), the retirement happens in two waves:
| Date | Milestone |
|---|---|
| September 2025 | First date-based CRM APIs (/2025-09/) debut at INBOUND 25 |
| March 30, 2026 | HubSpot introduces date-based API versioning across the platform |
| September 2026 | /2026-09/ versions ship at INBOUND 26; migration guide coverage expands |
| October 2026 (now) | "Apps with API versions to update" notices land in affected portals; audit tool available at Development → Migrations → APIs |
| March 2027 | /2027-03/ release: v4 APIs and the /2025-09/ CRM APIs are no longer supported |
| September 2027 | All legacy semantic-versioned APIs — v1, v2, v3, and v4 — are no longer supported |
Eleven months sounds comfortable until you subtract scoping, vendor response times, testing, and the change freezes most teams observe around year-end. A migration started in spring 2027 is a migration under pressure; one started this quarter is a line item.
Any portal with software that calls HubSpot's APIs is in scope. That includes private apps your own team built, custom integrations and middleware, and third-party apps installed from the marketplace or supplied by a vendor. HubSpot's migration guide calls out endpoint families that show up constantly in real-world portals: CMS blog posts, CMS site and landing pages, blog settings, templates, URL redirects, and site search — so content and website integrations are squarely in scope alongside CRM syncs. If your team runs a connected tech stack, like the ones we map in our guide to building HubSpot integrations for mid-market growth, assume at least one connection needs review.
This is why the notice belongs on an ops leader's desk, not only in a developer's inbox. The business owner of the portal often does not know which APIs their integrations call — and does not need to. HubSpot's in-app tool answers that question in plain terms: which apps, which endpoints, which sunset date, and how much recent call volume each one carries. Your job is to run the audit and route the results; your developer or vendor's job is the code change.
If the tool shows no apps, nothing calls legacy endpoints in your portal and no action is needed today.
HubSpot's recommended sequence is audit, map, migrate, test — in that order, and not in production first:
2026-09 and locate the matching operation. Many v3 and v4 endpoints have feature parity there.GET /crm/v3/objects/contacts → GET /crm/objects/2026-09/contacts
Do not assume the URL is the only change. Some endpoints changed request bodies, parameters, or response shapes between the legacy version and 2026-09, so compare the old and new reference pages field by field before cutting over.
2026-09 equivalent — or flagged as "no equivalent yet"/2025-09/ CRM APIs, and before September 2027 for everything elseSome older v1 and v2 endpoints do not have a date-based equivalent as of October 2026. HubSpot says the migration guide is updated regularly as those gaps close, so the correct posture is: migrate everything that has an equivalent now, track the short remainder against the guide, and raise any blocker with HubSpot support or your implementation partner so it is on record well before September 2027. Do not let a missing equivalent for one endpoint stall the migration of twenty that are ready.
Newer integration surfaces, like the HubSpot MCP server for AI CRM integration, build on the current platform — one more reason legacy surface area is shrinking rather than being maintained indefinitely.
For every external app on your audit list, send the vendor five questions:
/2026-09/), and if not, when will you?/2025-09/ CRM APIs) and September 2027 (all legacy APIs) deadlines?A vendor with no answer to the first two questions in late 2026 is telling you something about their maintenance posture. Factor that into renewal decisions.
Vantage Point is a HubSpot Solutions Partner, and API-driven integration work is core to our HubSpot consulting practice. We help ops leaders run the Migrations audit, separate internal from vendor-owned fixes, map legacy endpoints to their 2026-09 equivalents, and sequence the work against the March and September 2027 deadlines. Where the migration touches broader data flows, our system integration and data migration team handles the rebuild and testing, and our senior consultants validate the portal is clean before cutover. Senior consultants only — no junior handoffs; the experts you meet are the experts who deliver.
A working session with a senior Vantage Point consultant will turn your Migrations tool output into a prioritized migration plan — internal fixes, vendor asks, and a test-first cutover schedule. Talk to our team about a HubSpot integration review, or see how our managed services keep portals current as HubSpot ships new API versions every March and September.
September 2027 for all legacy semantic-versioned APIs (v1, v2, v3, and v4). Two groups lose support earlier: v4 APIs and the /2025-09/ CRM APIs sunset at the /2027-03/ release in March 2027. These dates come from HubSpot's migration guide, last updated September 15, 2026.
Date-based versioning names each API version after its release month in a /YYYY-MM/ format, such as /2026-03/ or /2026-09/, instead of semantic versions like v3. HubSpot introduced it on March 30, 2026; new versions ship twice a year (March and September), each version is immutable, and every version is supported for a minimum of 18 months.
Check the in-app audit tool at Development → Migrations → APIs. Portals with apps calling legacy endpoints receive an "Apps with API versions to update" notification, and the tool lists each legacy endpoint, its version, its sunset date, and recent call volume per app. If the list is empty, none of your apps currently call legacy endpoints.
Any integration still calling legacy endpoints after the sunset dates risks failing once support ends. The practical risk arrives sooner for v4 and /2025-09/ CRM APIs, which sunset in March 2027. Migrating to date-based endpoints — for many endpoints a URL change — removes the risk.
For many endpoints, it is a URL swap: GET /crm/v3/objects/contacts becomes GET /crm/objects/2026-09/contacts, with the version slug moving position in the path. Some endpoints changed request bodies, parameters, or response shapes, so compare fields one by one in the API reference before cutting over, and test in a HubSpot test account first.
Ask which HubSpot API version their app calls today, whether they have migrated to date-based endpoints, and when the migration will ship relative to the March 2027 and September 2027 deadlines. Also ask whether the update arrives as a normal product update and how they will confirm your account no longer appears in the Migrations tool.
Some older v1 and v2 endpoints do not have date-based equivalents yet, and HubSpot says the migration guide is updated regularly as gaps close. Migrate every endpoint that has an equivalent now, track the remainder against the guide, and raise the gap with HubSpot support or your partner so it is on record before September 2027.
Vantage Point is a boutique CRM consulting firm helping businesses transform with Salesforce, HubSpot, and AI. Learn more at vantagepoint.io.