Migrating to Checkout Extensibility Before the Deadline
Shopify is retiring checkout.liquid in favor of Checkout Extensibility. If your Plus store still relies on checkout.liquid customizations, you need a migration plan — and the upgrade is an opportunity, not just a compliance task.
Checkout Extensibility replaces script-based checkout edits with app-based UI extensions, Shopify Functions, and branding APIs. The payoff is a checkout that stays upgrade-safe, higher-converting, and eligible for Shop Pay and future Shopify features — none of which the legacy checkout.liquid guarantees.
What actually needs to move
- Custom fields and UI (gift messages, delivery notes) → Checkout UI extensions.
- Discount and shipping logic → Shopify Functions.
- Line-item and validation rules → Cart and Checkout Validation Functions.
- Branding and layout tweaks → the Branding API and checkout editor.
- Analytics and pixels → the Web Pixels API.
A safe migration sequence
- 1Inventory every existing checkout.liquid customization and the business reason behind it.
- 2Map each one to its Extensibility equivalent — and cut the ones no longer earning their keep.
- 3Rebuild in a draft/staging environment with UI extensions and Functions.
- 4QA across payment methods, discount stacking, and edge cases like B2B and multi-currency.
- 5Launch behind a controlled cutover, then monitor conversion and error rates closely.
Treat it as a conversion upgrade
The teams that get the most from this migration don't just port old customizations one-for-one. They use the move to simplify the flow, add one-click post-purchase upsells, and tighten trust signals — turning a forced upgrade into a measurable conversion win.
Don't migrate your old checkout. Rebuild the checkout you'd design today, then make it upgrade-safe.
Frequently asked questions
Who needs to migrate to Checkout Extensibility?
Any Shopify Plus store still using checkout.liquid or checkout script customizations. Standard (non-Plus) stores are already on the upgraded checkout.
Will migrating change how my checkout looks?
It can look identical, or better. Branding APIs and the checkout editor reproduce most existing styling, and the migration is a good moment to streamline the flow for higher conversion.
Can I keep my custom fields and upsells?
Yes. Custom fields move to Checkout UI extensions and upsells to post-purchase extensions. Most legacy customizations have a supported, upgrade-safe equivalent.