Checkout Extensibility, explained for store owners
Haniel Singh
Founder, Creative Labs · Published Sep 2026 · 2 min read
Summarize with AI
Shopify replaced checkout.liquid with Checkout Extensibility: apps and blocks that run inside the checkout without touching its code. It is faster, safer and the only option on Plus since August 2025.
Here is what that means if you run a Plus store, and what to do if your checkout still relies on the old customisations.
TL;DR
- •checkout.liquid is gone; customisations are now extensions, Functions and the branding editor.
- •You can add trust blocks, upsells, delivery pickers and custom fields without hurting speed.
- •Discount, shipping and payment logic moves into Functions, which run server-side.
- •Non-Plus stores get branding and Shop Pay; the rest needs Plus.
What changed and why
Old checkout customisations were scripts injected into a page Shopify had to keep stable, so every change was slow and risky. Extensibility gives apps and your developers fixed slots in the checkout and a UI toolkit, and Shopify keeps the page fast.
The practical effect: checkout changes ship in days, not weeks, and they survive Shopify’s updates.
- •UI extensions: blocks in fixed slots on each checkout step.
- •Functions: discount, delivery and payment logic, server-side.
- •Branding API: fonts, colours and layout from the admin.
What you can build now
The things that move completion rate: trust and delivery-date blocks where doubt appears, an order bump on the first step, express wallets first, gift and custom fields that validate before the shopper hits pay.
The things that protect margin: discount Functions that stack the way you want, delivery rules by cart contents, payment methods hidden for risky orders.
Want us to run the CRO sprint on your store?
Book a call →What it costs and who needs it
- 1.Plus: $2,300/mo and up; Extensibility is included.
- 2.A custom extension: $3,000–$8,000 built, usually inside a checkout sprint.
- 3.Non-Plus: use the branding editor and Shop Pay; most stores under $1M don’t need more.
- 4.Upgrade trigger: you have scripts or a checkout.liquid theme still running.
Frequently asked
Do we need Plus to customise checkout?
Will extensions slow down checkout?
Can we migrate our old checkout scripts?
Sources(6)
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Written by
Haniel Singh
Founder, Creative Labs
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