The Shopify checkout has always been one of the platform's strongest selling points — it converts well, it is trusted by consumers, and it handles the complexity of payments, tax, and fraud detection reliably.
The limitation, historically, was that merchants had limited control over how it looked and behaved. Checkout Extensibility, which became the standard approach in 2024, changed that significantly. Here is where things stand in 2026.
What Checkout Extensibility Allows
Checkout Extensibility (CE) is Shopify's framework for adding functionality to the checkout without modifying the underlying checkout code. Instead of editing checkout.liquid (which still requires Shopify Plus and is increasingly deprecated), CE allows merchants to add UI extensions — custom components built with Shopify's framework — to specific slots in the checkout.
What this enables:
Custom upsells at checkout. A post-purchase upsell that appears after payment but before the thank-you page, or a product recommendation block within the checkout itself. These can be targeted by cart contents, customer tags, or order value.
Loyalty programme integration. Displaying and redeeming loyalty points directly within the checkout, rather than requiring a separate redemption step before reaching checkout.
Custom form fields. Adding fields for gift messages, delivery instructions, or survey questions to the checkout. These fields can be attached to the order for fulfilment purposes.
Trust and benefit blocks. Adding trust signals — security badges, delivery promises, returns policy — directly within the checkout flow, at the points where hesitation is highest.
Subscription and upsell conversions. Offering a subscribe-and-save upgrade within the checkout for one-off purchasers.
What Requires Shopify Plus
Some checkout customisation capabilities are gated to Shopify Plus:
Checkout branding. Changing fonts, colours, and brand elements within the checkout (beyond the basic logo and button colour available on standard plans) requires Plus.
Checkout Extensibility with full slot access. Standard plan merchants can use some CE extensions; Plus merchants have access to all checkout slots and advanced extension capabilities.
Script-based customisation. Older Shopify Scripts (which manipulate line items, shipping, and payment methods) were Plus-only and are being phased out in favour of CE-compatible alternatives.
If checkout customisation is a core reason you are considering Shopify Plus, map your specific requirements against what CE supports on standard plans first. Some requirements that previously needed Plus can now be addressed without it.
The Thank-You Page and Post-Purchase
The thank-you page — the page shown after a successful order — is the highest-traffic page on most Shopify stores that almost no one optimises.
Post-purchase extensions available via CE allow merchants to:
- Present a one-click upsell (add to the same order with one tap, charged to the same payment method)
- Offer a referral or loyalty programme enrolment
- Present a survey question
- Display personalised product recommendations for a future purchase
The post-purchase upsell is particularly valuable because the customer has already committed to buying. The psychological barrier is much lower than convincing a new visitor to add something to their cart.
Common Mistakes in Checkout Customisation
Adding too much. Every addition to the checkout is a potential distraction from completing the purchase. A checkout loaded with loyalty prompts, upsells, survey questions, and trust badges becomes overwhelming. Prioritise one or two extensions with clear conversion goals.
Upsells that are irrelevant. A checkout upsell that bears no relation to what the customer is buying is almost always ignored and can create a jarring experience. Target upsells by cart contents — if someone is buying a camera, suggest a memory card, not a candle.
Forgetting mobile. CE extensions need to be tested on mobile. An upsell that looks elegant on desktop can be awkward and disruptive on a phone screen.
Building CE Extensions
CE extensions are built with JavaScript using Shopify's Checkout UI Extension framework. The development experience is well-documented and growing more capable with each update.
For merchants without in-house development resource, several Shopify apps provide pre-built CE extensions for common use cases — post-purchase upsells, custom fields, loyalty integrations — that can be configured without code.
For more bespoke requirements, a Shopify developer can build custom extensions to your specification.
Checkout Extensibility represents a genuinely significant improvement in what Shopify merchants can do with their checkout. The question is not whether to use it but which extensions are worth implementing for your specific store and customer base.
If you want help planning and implementing checkout customisation for your Shopify store, get in touch.