HubSpot Developer Deadlines for Business Owners: Oct 26, Nov 2 and 2027

If your HubSpot account passes data to your accounting system, billing tool, website or reporting dashboards, it’s worth checking whether those connections use parts of HubSpot that are being retired.

HubSpot announced the changes in its developer changelog, and the first date is Monday, October 31, 2026.

Nothing switches off on that day. Existing connections keep running. What changes is how you build, rebuild or repair them, and by September 2027 the old versions stop being supported at all.

This guide lists the dates, explains what each one means in plain terms, and gives you a short checklist to run with whoever looks after your integrations.

The Dates at a Glance

Private Apps: the Change on October 26

A private app is a set of credentials an admin creates in HubSpot settings so another system can read or update records. Our own guide to finding your HubSpot API key walks through creating one.

HubSpot is removing the option to create new legacy private apps from the account settings.

This applies to every HubSpot account, not only to Marketplace apps.

For accounts created before September 28, 2026, the option goes away on October 26, 2026.

HubSpot states that “All existing legacy private apps continue to work as-is.”

The cutoff matters when something needs to be created again. One developer on HubSpot Community forum put it this way:

“A setup can run fine today but still be imposible to recreate after a sandbox refresh if part of the provisioning path depends on creating a legacy private app.”

HubSpot Community, Oct 4, 2026

In business terms: if a connection breaks, or your developer refreshes a test account, or you add a new connection after October 26, the old setup route isn’t available.

The work has to use one of HubSpot’s current options:

• • Service keys, for straightforward system-to-system connections. HubSpot lists scoped access, built-in activity logging, key rotation with a 7-day grace period and admin-only key visibility. Integrations keep working if the person who created the key leaves. Service keys only make REST API requests: they don’t support webhooks (instant notifications when a record changes) or UI extensions, so they don’t fit every connection. HubSpot Fall 2026 release notes list service keys as a public beta, while HubSpot service key documentation (updated Sept 30, 2026) no longer calls them beta. Check HubSpot changelog for the current status before you rely on them in production.
  • A project-based app, built with HubSpot developer tools, for connections that need webhooks or other app features.

Legacy CRM cards: the change on November 2

Some apps show a custom information panel on HubSpot records, for example an order history or billing status on a company record. Panels built the old way, called legacy CRM cards, are removed from users’ record views on November 2, 2026, according to HubSpot’s current migration guide. (HubSpot’s 2025 announcement gave October 31, 2026.) HubSpot’s replacement is the app card.

Two points from HubSpot’s documentation matter for planning:

• Developers can keep running the migration until December 1, 2026. After that, HubSpot discontinues the migration tool.
• Once the migration of card views has started, “it cannot be reversed”. HubSpot recommends testing the new app card before replacing the old one in all user views.

If a card your team uses comes from a Marketplace app, the vendor handles the migration. If it was custom-built for you, someone on your side has to do it.

Old API versions: the 2027 deadlines

HubSpot now uses date-based API versions (for example 2026-09) instead of numbered ones (v1 to v4).

For the numbered versions, HubSpot says it “will no longer release bug fixes, reliability improvements, or security updates” for v1 to v3, and they become unsupported in September 2027. v4 goes unsupported earlier, in March 2027.

HubSpot’s pages don’t yet agree on the exact v4 date: the v4 changelog shows both March 1 and March 30, 2027, and the migration guide groups v4 with September 2027. HubSpot also says unsupported versions “may continue to function for some period of time, but they are not guaranteed to remain stable or available.” HubSpot’s advice is to move directly to the date-based version, not to v3 or v4 as a stop on the way.

For many endpoints the change is just a new web address. HubSpot’s own example turns /crm/v3/objects/contacts into /crm/objects/2026-09/contacts. Others change what they accept or return, so each one needs testing. And HubSpot states that “some older v1 and v2 endpoints may not have exact date-based equivalents at this time.” If your integration depends on one of those, your developer needs a fallback plan, not just a find-and-replace. Our explainer on the HubSpot Associations API covers one area where v3 and v4 differ.

Two cautions from developers on HubSpot Community forum:

• One app partner found that his account migration tool showed March 1, 2027 for v4, while the changelog text says March 30. A reply on HubSpot behalf said: “I’ve also flagged the discrepancy between the migration tool and the changelog so that our team can make the necessary corrections.” Plan for March 1 until HubSpot confirms.
• HubSpot’s migration tool detects old API calls “at runtime, not your source code”. So a call that runs rarely, such as a month-end sync, may not appear in the list until it has run.

If you rely on Marketplace apps

September 2027 rules also apply to apps on the HubSpot Marketplace.

Apps that still use unsupported API versions (v1 to v4) after September 2027 lose their certification, and apps still on the old app architecture are “eligible for delisting.”

Thats the vendors work, not yours, but it’s fair to ask each vendor you depend on when they’ll be migrated.

The October 26 Marketplace change is narrower than it sounds.

It only applies when a vendor edits its listing, and HubSpot documentation says existing installs and installs started outside the Marketplace aren’t affected.

A HubSpot Community team member summed it up: “The OAuth process itself is not changing.”

A Checklist to Run with Your Developer

1. List every connection to HubSpot. For each one, write down what it does, which system is on the other end, who built it and who looks after it now.
2. Open HubSpot migration tool. In your HubSpot account, go to Development > Migrations and open the APIs tab. It shows the old API calls HubSpot has seen from your account.
3. List your private apps. Note which ones were created the legacy way and which integrations depend on each.
4. Check custom record cards before the end of October. Find out whether each one is from a Marketplace vendor or custom-built.
5. Test a rebuild, not just the endpoints. Developers on HubSpot’s Community forum recommend proving you can recreate each connection from scratch with the supported setup, including after a test-account refresh.
6. Flag anything with no replacement yet and agree a fallback.
7. Put a date on each item. Work back from November 2, 2026 for cards, March 1, 2027 for v4 and older Projects versions, and September 2027 for everything else.