Polaris Web Components Migration: Shopify Checkout & Customer Account

Shopify has changed the core architecture of UI extensions for Checkout and Customer Account. This is not an incremental update: the development model changes in a fundamental way, and the official migration guides to Polaris web components are now available on shopify.dev.

If your extensions are using an API version earlier than 2025-10, migration is mandatory to avoid active deprecations at the most critical conversion point in any store.

What changes in the architecture

Until now, Checkout and Customer Account extensions could be built with React or vanilla JavaScript through Shopify's APIs. With version 2025-10, this paradigm is being abandoned.

The new stack is built on three core elements:

• Preact instead of React as the rendering library
• Polaris web components as the standard UI component system
• The global shopify object for access to platform APIs

This change is not just about syntax. It affects how components are instantiated, the extension lifecycle, and how extensions interact with the checkout context.

Components affected by the migration

Shopify has published over 60 documentation pages dedicated to component-by-component migration. Among the main components that require a rewrite:

• Button: new API for events and variants
• TextField: revised state management and validation
• Banner: completely redefined structure and props
• Checkbox: updated form state integration
• View: layout and composition with a new model

Taking an existing extension that uses Banner to display promotional messages at checkout and adapting it to the new system is not a superficial refactor: it requires a rewrite guided by the new component API, with testing against real checkout behavior.

Metafield migration: a separate risk

One aspect that risks being underestimated involves metafields. Existing checkout metafields must be migrated to cart metafields. This is a change with direct operational impact: if metafields are used to pass custom data between the frontend and backend during checkout, an incomplete migration can cause data loss or unexpected behavior on orders.

This point should be planned separately from the UI component migration, with dedicated testing in a staging environment before any production deploy.

How to proceed: operational priorities

If you manage Checkout or Customer Account extensions, the recommended path is as follows:

1. Check the API version of each active extension. Extensions running on versions prior to 2025-10 are the ones exposed to deprecation risk.
2. Prioritize production extensions, especially those operating directly within the purchase flow.
3. Follow the component-by-component migration using the official shopify.dev guides, without attempting unstructured global rewrites.
4. Plan the metafield migration as a separate activity, with a dedicated validation phase.
5. Test in a controlled environment before releasing to live stores, especially for Shopify Plus merchants with highly customized checkouts.

Impact on Shopify Plus merchants with custom checkouts

For those managing multiple Shopify Plus merchants, the overall effort can be significant. Every store with custom checkout extensions requires an individual assessment: the number of components to migrate, the complexity of the implemented logic, and the presence of custom metafields all determine the actual volume of work.

Staying on a previous API version is not a neutral strategy: it means exposing yourself to active deprecations on a component that is critical to conversion rate. Teams that plan the migration now have the advantage of handling it calmly, without having to operate under pressure when legacy versions are disabled.

For an assessment of the specific effort required for your Shopify project, see the Shopify developer plans available on Barikreativa.

Polaris web components as a long-term standard

Beyond the immediate migration, the adoption of Polaris web components represents Shopify's strategic direction for UI extensions. Investing in the rewrite now means aligning with a stack that will receive support and updates over the medium to long term, rather than maintaining code on an architecture that is being phased out.

The official documentation is available on shopify.dev and covers every component in detail, with before-and-after code examples for the migration.