How can we integrate custom functions into the checkout extensibility feature?

Technical Q&A

Topic summary

A developer is seeking guidance on migrating existing custom checkout functionality to Shopify’s checkout extensibility feature. They have three main questions:

Key Questions:

  • Whether separate APIs exist for this feature or if it uses the same checkout APIs
  • If they need to create an app to edit the checkout extensibility feature
  • What APIs are available to access or update this checkout feature

The post appears garbled in parts (possibly encoding issues), but the core concern is understanding the technical requirements and API structure needed to implement custom functions within Shopify’s checkout extensibility framework. No responses or solutions have been provided yet.

Summarized with AI on November 22. AI used: claude-sonnet-4-5-20250929.
1

We need help related to checkout extensibility feature. we going to use checkout extensibility feature but our checkout have some custom functionality then how can we move that in this feature.

  1. is there any API to access or update this checkout feature.
  2. do we have to create app to edit this checkout extensibility feature.
  3. is there any separate API’s for this feature or it is using same checkout API’s.