Shopify Checkout Extensibility: What You Can Customize in 2026

For years, customizing Shopify checkout meant one thing: editing a file called checkout.liquid, which only Shopify Plus stores could access. That era is over. The old file has been retired step by step, and the last deadline passed in August 2026.

Its replacement is checkout extensibility, a set of tools that let you brand checkout, add features, and change how it behaves, without editing the checkout's code directly.

If you're wondering what you can actually change in 2026, and whether you need Shopify Plus to do it, this guide answers both in plain language.

The Short Answer

Shopify checkout extensibility lets you customize checkout through the checkout and accounts editor, apps, checkout UI extensions, Shopify Functions, and pixels. On every plan from Basic up, you can brand your checkout and add apps to the Thank you and Order status pages. Customizing the Information, Shipping, and Payment steps with apps, and using the full Checkout Branding API, requires Shopify Plus.

What Is Checkout Extensibility?

Checkout extensibility is Shopify's current way of customizing checkout. Instead of editing one big code file, you customize checkout through defined, upgrade-safe tools: an editor for branding and layout, apps and extensions that add blocks to specific places, and Functions that change business logic like discounts and delivery options.

Shopify's Help Center describes the checkout and accounts editor as a single place to customize the checkout, Thank you, Order status, and customer account pages, separate from your theme editor.

The benefit is stability. Because customizations plug into defined spots, Shopify can keep improving checkout without breaking your changes, which was a common problem with checkout.liquid.

What Happened to checkout.liquid

Shopify retired checkout.liquid in stages. According to Shopify's developer documentation:

Shopify Scripts, the Ruby code Plus stores used for checkout discounts and rules, also stopped running on June 30, 2026, and were replaced by Shopify Functions.

In practice, this means every Shopify store now runs on checkout extensibility. If tracking codes or custom content used to live in the "additional scripts" box, they need to be rebuilt with apps, extensions, or pixels.

The Building Blocks

Checkout extensibility is really five tools working together. Knowing which one does what makes planning much easier.

1. The checkout and accounts editor. This is where you change how checkout looks: your logo, background color or image, colors, and fonts across the checkout, Thank you, and Order status pages. Shopify notes that some of these branding choices also apply to your customer account pages. It's also where you place app blocks onto the page.

2. Checkout apps and UI extensions. Apps from the Shopify App Store, or custom apps built for your store, can add blocks to checkout pages. Shopify's example is an upsell app placed in the order summary, so shoppers can add items during checkout. Other common blocks include delivery date pickers, gift messages, loyalty points, and trust messages. Under the hood, these are called checkout UI extensions.

3. The Checkout Branding API. For deeper visual control than the editor offers, such as detailed typography, spacing, and component styles, developers can use this API. Shopify lists it as a Shopify Plus feature.

4. Shopify Functions. Functions change checkout logic rather than appearance: discounts, which shipping options appear, which payment methods appear, and cart validation rules. They're packaged inside apps. Public apps that use Functions work on any plan; custom apps containing Functions require Shopify Plus.

5. Pixels for tracking. Analytics and marketing tracking that used to sit in "additional scripts" now runs through Shopify's pixel system, set up through apps or custom pixels in your Customer events settings.

What You Can Customize on Each Plan

This is the question most merchants ask first. Here's the breakdown, based on Shopify's checkout customization comparison and its Function APIs documentation.

In short: every store can brand checkout, customize the pages after purchase, and use public Function-based apps. Changing what shoppers see and do during the actual checkout steps, before they pay, is where Shopify Plus comes in.

If that's the deciding factor for your business, our guide to [Shopify vs Shopify Plus in 2026](BLOG #1 URL) covers the wider upgrade decision.

Common Use Cases, and Which Tool Handles Each

Shopify's Help Center also notes you can adapt checkout pages for specific markets, which is useful if shoppers in different countries need different messages or options.

What You Still Can't Do

Checkout extensibility is flexible, but it isn't a blank canvas. Knowing the limits upfront avoids designing something that can't be built.

• You can't rewrite checkout's underlying code. Customizations go into defined spots, not anywhere you like. Design work should start from how Shopify checkout is structured, not from a fully custom layout.

• You can't add apps to the Information, Shipping, and Payment steps without Shopify Plus. On other plans, these steps can be branded but not extended with apps.

• You can't paste scripts into checkout anymore. The old "additional scripts" approach is gone. Tracking moves to pixels, and custom content moves to apps or extensions.

• Custom Functions need Plus. If no public app handles your discount, delivery, or payment rule, a custom-built Function requires Shopify Plus.

• Shopify Scripts are gone. They stopped running on June 30, 2026. Any logic still relying on them needs rebuilding with Functions. Our guide to [rebuilding checkout logic with Shopify Functions](BLOG #2 URL) explains how.

The practical approach is to work with your developer to confirm what's possible before designing new checkout features, rather than designing first and discovering limits later.

How to Plan Checkout Changes Without Hurting Conversion

Checkout is the most sensitive part of your store. Shoppers who reach it already want to buy, so every addition should earn its place.

1. Start with a reason, not a feature. Look at your data and customer questions first. Are shoppers abandoning at shipping? Asking about delivery dates? Missing a discount field? Build changes that answer a real problem.

2. Keep it short. Every extra field, banner, or upsell adds something to read or decide. One relevant upsell is easier for shoppers to act on than several competing offers.

3. Put post-purchase offers on the Thank you page. Surveys, referral offers, and reorder prompts don't distract buyers before they pay. These pages are also available on every plan.

4. Test before you publish. Shopify's Help Center describes managing active and draft checkout configurations, so you can prepare changes before making them live. Shopify's Rollouts feature also supports scheduling and A/B testing checkout configurations, according to its changelog.

5. Check mobile first. Many checkout problems show up on small screens: crowded layouts, hard-to-tap fields, and messages that push the pay button down.

6. Place test orders. After every change, run a test order through each payment method and shipping option you offer.

7. Measure the result. Compare checkout completion rate and average order value before and after each change, and remove anything that isn't helping.

App or Custom Build?

For most checkout features, start by looking for an app. Shopify maintains a collection of checkout apps in the App Store, and many common needs are already covered.

Choose an existing app when:

• The feature is common, such as upsells, gift messages, delivery dates, or post-purchase surveys

• You want to launch quickly

• The app's settings let you match your brand and rules

Consider a custom build when:

• Your rule or feature is specific to your business and no app handles it properly

• You're stacking several apps to get one result

• Checkout needs to use data from another system, such as B2B pricing or credit limits from your ERP

• You want full control over how the feature looks and behaves

Remember the plan limits: custom checkout UI extensions for the steps before payment, and custom apps containing Shopify Functions, both require Shopify Plus.

Our guide to [choosing between a public app, a custom app, or theme code](BLOG #9 URL) explains the trade-offs in more detail.

Frequently Asked Questions

What is Shopify checkout extensibility?

It's Shopify's current way of customizing checkout, using the checkout and accounts editor, apps and checkout UI extensions, Shopify Functions, and pixels. It replaced checkout.liquid, which has now been fully retired.

Can I customize Shopify checkout without Shopify Plus?

Yes, partly. On Basic plans and above, you can brand your checkout in the checkout and accounts editor, add apps to the Thank you and Order status pages, and use public apps built on Shopify Functions. Adding apps to the Information, Shipping, and Payment steps requires Shopify Plus.

Is checkout.liquid still supported?

No. It's unsupported for the Information, Shipping, and Payment steps, and was retired for the Thank you and Order status pages on August 28, 2025. Script tags on those pages were retired for Plus stores on August 28, 2025, and for non-Plus stores on August 26, 2026.

Where do I add tracking scripts now?

Tracking that used to sit in "additional scripts" now runs through Shopify's pixel system, set up with apps or custom pixels in your Customer events settings.

Can I add an upsell to Shopify checkout?

Yes. On Shopify Plus, upsell apps can add blocks to the checkout steps, such as the order summary. On other plans, upsells can appear on the Thank you page after purchase.

Do I need a developer to customize checkout?

Not always. Branding in the checkout and accounts editor, and installing apps, can be done without code. You'll need a developer for custom extensions, custom Functions, or Checkout Branding API work.

Planning Checkout Changes?

CodeVibez is a Shopify Plus Preferred Partner that has supported more than 1,000 Shopify stores across D2C, B2B, and wholesale. We help brands plan and build checkout customizations, from branding and post-purchase pages to custom checkout extensions and Shopify Functions, and we'll tell you honestly when an existing app is the better choice.

If your checkout plans need Shopify Plus, our Shopify Plus development team can take it from there.

Schedule a free call or contact our team.