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Engineering the Business·Episode 4·Series

HubSpot UI Extensions

Building custom cards inside the CRM

Apr 14, 2026·41:40·Buzco Stanislav, Paul Maxwell

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About this episode

Paul and Buzco build a custom HubSpot UI extension live: rendering data, wiring actions, and shipping a card that lives right inside the record. Includes a working code sample.

Key ideas

  • 01UI extensions put custom logic where reps already work
  • 02Native-feeling extensions get used; bolted-on ones get routed around
  • 03Lean on the design system and keep interactions predictable
  • 04Make write-back actions explicit and safe

Show notes

What we covered

UI extensions let you bring custom functionality directly into the HubSpot record view, where reps actually work. Paul and Buzco build one from scratch, covering the SDK, data fetching, and the design choices that make an extension feel native. A code sample is included.

In this episode

  • What UI extensions are and where they fit
  • Setting up the developer project and SDK
  • Fetching and rendering CRM data in a card
  • Wiring up actions that write back safely
  • Design choices that make extensions feel native

Links & resources

  • UI Extensions Code Sample (downloadable)
  • HubSpot UI extensions documentation
  • Buzco on building native-feeling cards

Timestamps

Chapters

  1. —Why UI extensions
  2. 7:00Project and SDK setup
  3. 16:40Fetching and rendering data
  4. 26:40Wiring actions safely
  5. 35:00Making it feel native

Quotable

“If your extension feels native, reps just use it. If it feels bolted on, they route around it.”

— Paul Maxwell

Full transcript

Transcript~1 min read

Show transcriptHide transcript

Paul: UI extensions are underrated because they put your custom logic exactly where the rep already is, on the record. No context switch, no separate tool, no tab-hopping.

Buzco: And the SDK is genuinely nice to work with now. You fetch your data, render a card, wire an action, and it lives inside HubSpot like it was always there.

Paul: The trick is making it feel native. If your extension looks and behaves like the rest of the CRM, reps just use it. If it feels bolted on, they route around it.

Buzco: So we lean on the design system, keep the interactions predictable, and make writes explicit. In the code sample you'll see exactly how that action wiring works.

Mentioned

  • HubSpot
  • React

Related links

  • HubSpot UI extensions docs

Hosts

  • BS
    Buzco Stanislav

    Host

    CTO, RevOps HQ

  • PM
    Paul Maxwell

    Host

    CEO, RevOps HQ

Topics

  • HubSpot
  • Software Engineering
  • UI Extensions

Downloads & resources

  • HubSpot UI Extensions Code SampleCode Sample

Subscribe to Engineering the Business

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  • Spotify

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