HubSpot Ends Support for Legacy APIs & Apps by Sept 2027
HubSpot announced on September 15, 2026 that it will end support for its v1-v3 APIs, legacy public apps, and legacy private apps, with enforcement scheduled for September 2027. The breaking-change notice published by HubSpot gives developers a 12-month migration window, while Megachangelog’s independent record confirms the same scope and deadline. (developers.hubspot.com)
HubSpot will retire v1-v3 APIs by September 2027
HubSpot’s announcement covers API versions that use numbered paths such as `/v1/`, `/v2/`, and `/v3/`. Those endpoints will move to unsupported status and will eventually be removed after September 2027, with no further bug fixes, reliability improvements, or security updates during the unsupported period. Developers are expected to migrate directly to HubSpot’s date-based API versions rather than using v3 or v4 as an intermediate step. (developers.hubspot.com)
The deadline is separate from the previously announced v4 timeline. HubSpot plans to end support for current v4 APIs on March 30, 2027, while the September 2027 enforcement applies to the older v1-v3 versions and the legacy app architectures covered in the new announcement. (developers.hubspot.com)
Legacy public apps face Marketplace certification risk
Public apps created before June 23, 2026 use HubSpot’s pre-Projects architecture. They must move to the current Projects-based model to remain supported, retain Marketplace certification, and avoid possible delisting when enforcement begins in September 2027.
The two migration requirements are independent. An app that moves to Projects but continues calling unsupported API versions can still lose certification. An app that updates its API paths but remains on the legacy app architecture can still become eligible for delisting. That makes the deadline more than an endpoint update because developers must review both the application structure and the API traffic behind it. (developers.hubspot.com)
Existing legacy private apps must move beyond the creation cutoff
The September 2027 deadline extends the impact beyond HubSpot’s earlier announcement about stopping new legacy private app creation. New accounts lose access to legacy private app creation on September 28, 2026, while existing accounts lose that creation path on October 26, 2026. Those dates stop new creation, but the September 2027 enforcement date applies to older private apps that remain on the legacy model.
For new lightweight, account-level integrations, HubSpot recommends Service Keys through Developer Platform Projects. Existing legacy private apps need to migrate to Projects-based private apps instead of treating the creation cutoff as the full deprecation event. (developers.hubspot.com)
HubSpot will detect legacy API usage at runtime
HubSpot’s Developer Home now identifies apps that call APIs becoming unsupported, but the detection checks runtime API traffic rather than relying only on source-code inspection. That distinction matters for integrations where an older endpoint is called through a shared library, background job, middleware service, or generated client.
The immediate implementation task is therefore two separate audits: identify every live call to v1-v4 endpoints, then confirm whether each public or private app uses the Projects-based architecture. HubSpot says complete replacement documentation for every legacy endpoint is expected with the March 2027 developer release, leaving teams with a migration window but not yet a finalized replacement map for every API surface. (developers.hubspot.com)
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