Checkout UI Extension useCustomer doesn't update on "known customer"

Shopify Apps

Topic summary

A developer is experiencing issues with Shopify’s useCustomer hook in a Checkout UI Extension.

The Problem:

  • The hook returns undefined when a returning customer enters their email at checkout, despite not being logged in
  • According to Shopify’s Buyer Identity documentation, useCustomer should return data for “known customers” of the shop
  • The developer interprets this to mean the hook should work for returning customers even without login

Goal:
Retrieve customer data (specifically metafields) based solely on email address during checkout

Status:
The issue remains unresolved. A second user has confirmed experiencing the same problem with the useCustomer() API, asking if any workarounds exist. No solutions have been provided yet.

Summarized with AI on October 30. AI used: claude-sonnet-4-5-20250929.
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Context

I’m working on a Checkout Extension UI app, and I need to get customer information when the purchaser enters their email.

The issue

According to the Buyer Identity docs, the useCustomer hook:

Returns the current Customer. The value is undefined if the buyer isn’t a known customer for this shop or if they haven’t logged in yet.

If I enter the email of a returning customer, the phrase “known customer for this shop” seems to indicate that the customer would be returned, even if they aren’t logged in.

It does not work.

Is there a way to retrieve customer data based solely on the email? Specifically, I need to retrieve a customer’s metafields

1 Like
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Hi, any workaround for this? I’m not able to make the useCustomer() api work as well.