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Your HubSpot Sidebar Might Go Blank

Oct 15, 2026

Reading time: 9 min

Laptop showing a HubSpot-style CRM record with an empty sidebar and a green card being dragged in to replace legacy CRM cards

Here’s how Monday, November 2 could start for a lot of HubSpot teams. A sales rep opens a deal ten minutes before a call. Usually the right sidebar shows the customer’s open invoices, pulled live from the billing system. This time that space is empty. No error, no warning banner. The panel is just not there.

Nothing will have broken over the weekend. HubSpot ends support for legacy CRM cards on Saturday, October 31, and if the invoice panel is one of them, this is exactly how it goes.

If your team relies on custom panels inside HubSpot records, this guide is for you. It covers what is changing, how to tell whether your portal is affected, and what to do before the deadline. [link: HubSpot services page]

What HubSpot legacy CRM cards are, and what changes on October 31

A CRM card is a panel on a contact, company, deal or ticket record that shows data from outside HubSpot: order history from your ERP, subscription status from a billing tool, shipment tracking. Some cards also had buttons, like “create invoice” or “sync to warehouse.”

The old version, which HubSpot now calls classic or legacy CRM cards, worked in a simple way. Every time someone opened a record, HubSpot sent a request to your server with the record’s ID and a few of its properties. Your server answered with a small block of JSON: up to five items, each with a title, a few fields and optional buttons. HubSpot drew the panel from that answer. If your server took longer than five seconds, the card stayed empty.

HubSpot stopped accepting new legacy cards in June 2025 and gave existing ones an end date: October 31, 2026 [ext link: HubSpot developer changelog, “Deprecating support for classic CRM cards”]. HubSpot’s migration guide adds two more dates. Legacy cards are removed from customer views on November 2, and the migration tools stop working on December 1 [ext link: HubSpot developer docs, “Migrate legacy CRM cards to app cards”].

The replacement is called app cards, part of what HubSpot calls UI extensions. They are built in React, run on HubSpot’s newer developer platform, and can do far more than the old panels: tables, forms, images, filters, writing data back. They are also a different piece of software. There is no switch that turns one into the other.

Why this change is easy to miss

Most platform changes make some noise: emails to admins, a banner in the portal, a workflow that starts failing. This one stays quiet, for two reasons.

Legacy cards belong to apps, not to your portal. If a developer or an agency built an integration for you a few years ago, the card lives in that app’s code. Your HubSpot admin may never have seen the word “legacy” anywhere.

And when the card goes, it leaves no trace. There is no error on the record. The panel disappears, and most people will assume someone changed the layout. In a lot of companies the first report will be a rep asking in Slack where the invoice panel went, a week after it happened.

How to check if your portal uses HubSpot legacy CRM cards

Four checks. The first two take about ten minutes.

1. Open a few records and look at the sidebars. One contact, one company, one deal, one ticket. Write down every panel that shows data from another system. Those are your candidates.

2. Match each panel to an app. Open the list of connected apps in your HubSpot settings and note where each panel comes from. Split them into two groups: apps from the HubSpot Marketplace, and apps built for you by your team, a freelancer or an agency.

3. For Marketplace apps, ask the vendor. One email is enough: “Have you migrated your CRM card to app cards before October 31?” Serious vendors finished this months ago. If the answer is vague, plan for the panel to disappear.

4. For custom apps, ask whoever maintains the code. A developer can confirm it in a few minutes. Legacy cards are set up with a “data fetch URL” in the app’s settings and managed through HubSpot’s CRM extensions cards API. If the app is also still on HubSpot’s older app model, that is a second job for the same list.

HubSpot deal record sidebar with a custom CRM card that pulls data from an external system

What a migration actually involves

If you have a custom card, here is what the work looks like from the inside. It helps to know this before you ask for a quote.

The app moves to the new platform. App cards only run in apps built on HubSpot’s projects framework, version 2025.2 or later. An older app has to move there first.

The card is rebuilt in React. The old card was a JSON answer. The new one is a small React component that uses HubSpot’s UI library. For simple cards, HubSpot published a converter sample that recreates the old layout, which makes a decent starting point.

The data logic changes place. The new card still gets data from your systems, but through HubSpot’s own fetch or serverless functions, instead of HubSpot calling your server directly. Authentication and secrets have to be set up again.

The views are swapped. HubSpot provides a tool that replaces the legacy card with the new one in every portal where the app is installed, in the same spot on the record. This step can’t be stopped or undone, so the new card has to be tested before you run it.

A concrete example. Say a manufacturer has a card on company records that shows the last five orders from their ERP, plus a “reorder” button. Five, because that was the old limit. The new card can show a sortable table of the last 50 orders with a status filter, and the reorder button can open a short form instead of firing straight away. If you scope it that way, the migration is also a chance to fix what people disliked about the old panel.

On our side, the slowest part of this work used to be reading integration code nobody had touched in years. Now we give an AI model the old endpoint and a sample of its JSON responses, and ask it to list every field, action and edge case the card handles, then draft the React component against HubSpot’s UI library. A developer checks that list against the real code and finishes the component. The review stays with a person. The digging takes a fraction of the time.

How long it takes, and what to do before the deadline

A simple card that shows a few fields usually takes a few days of development and testing. A card with buttons, several record types or helpdesk tickets (which need a separate version of the card) takes longer, often one to three weeks, especially if the app first has to move to the new platform.

With the deadline close, sort your cards:

Cards your team opens every day (billing, orders, subscriptions): migrate now.
Cards used now and then: rebuild right after the deadline. The migration tools stay available until December 1, so a short gap is survivable if your team knows about it.
Cards nobody opens: let them go.

Then tell your sales and support teams which panels may disappear on November 2 and where to find the same data in the meantime. Two lines in a team channel will save you a pile of confused tickets.

When you don’t need to rebuild a card

Some cards were built years ago for problems HubSpot now solves on its own. If a card only shows a few fields from another system, a regular sync into HubSpot properties may be simpler. The data then lives on the record, works in reports and workflows, and doesn’t depend on a live request every time someone opens a page.

App cards earn their cost when the data changes often, sits in a system you don’t want to copy into HubSpot, or when people need to act on it from the record. If none of that applies, a sync (or nothing) is probably the better choice. We’ll tell you which one on the first call.

FAQ

What happens to legacy CRM cards after October 31, 2026?
They stop rendering. HubSpot’s migration guide says they are removed from customer views on November 2, 2026. Users see the record without the panel and no error message.

Does this affect apps from the HubSpot Marketplace?
Yes, if the vendor hasn’t migrated. Existing Marketplace apps had until October 31, 2026 to move their cards. Check with each vendor.

Can I still migrate after the deadline?
HubSpot’s migration tools stay available until December 1, 2026. The old cards will still be gone from records in the meantime.

Can a migration be undone?
No. Once the view swap starts, it can’t be stopped or reversed. Test the new card first.

What replaces legacy CRM cards?
App cards: React components that run inside apps built on HubSpot’s projects framework, version 2025.2 or later.

Check your HubSpot legacy CRM cards this week

You have until Saturday, October 31, and realistically until Monday morning, when your team opens their first deal of the week. Ten minutes in the sidebars will show you whether HubSpot legacy CRM cards are part of your setup. If they are, sort them by how often people use them and start with the one your sales team would miss first. [link: related article on HubSpot integrations]

Not sure which panels in your portal are legacy? Send us a screenshot of a deal record and your list of connected apps. We’ll tell you what needs migrating and roughly how long it will take.

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