Shopify Checkout Extensibility 2026: After the Deadline

Shopify Checkout Extensibility in 2026: What Changed After the checkout.liquid Deadline

TL;DR: checkout.liquid is no longer supported anywhere in Shopify checkout. For Shopify Plus, the Information, Shipping and Payment steps moved first (August 13, 2024), and the Thank you and Order status pages followed on August 28, 2025. Plus stores that hadn't migrated started being upgraded automatically from January 2026, and their legacy customizations were removed, not migrated. Non-Plus stores had until August 26, 2026 to upgrade their Thank you and Order status pages. What replaces it is Checkout Extensibility: checkout UI extensions, Shopify Functions and web pixels. They're upgrade-safe and sandboxed, and they're a real chance to rethink your checkout. Winsomies, a Shopify app studio and development partner, can help you rebuild.

For years, Shopify checkout was a secure but rigid "black box". Plus merchants could edit checkout.liquid, and everyone else mostly lived with the defaults. That era is over. The deadlines have passed, and every store now runs on the same modern foundation.

If your migration happened in a hurry, or Shopify upgraded you automatically, there's a good chance your checkout is now more basic than it used to be. The good news is that checkout extensibility makes it easier than ever to build it back better.

The Deadlines: What Happened and When

Sources: shopify.dev, checkout.liquid and the Shopify Help Center.

What Happens Now That the Deadlines Have Passed

Legacy customizations are gone or frozen

Shopify's help docs say that when you upgrade, your existing Thank you and Order status pages and any customizations on them are replaced with the new versions. Automatic upgrades work the same way: they clean up, they don't migrate.

Additional Scripts are view-only

Since August 28, 2025, the additional scripts section in Checkout settings has been view-only. You can read what's there, but you can't edit it. Anything it did, from tracking to page tweaks, needs to be rebuilt with apps, blocks or pixels.

Tracking may have gaps

If your GA4, Meta or other conversion tracking lived in additional scripts or checkout.liquid, audit it now. Shopify recommends app pixels and custom web pixels for tracking customer events on the new pages.

Your checkout may look generic

An automatic upgrade gives you the standard Shopify checkout. It's fast and reliable, but it may be missing the branding, messaging and features you used to have.

How to check: in your Shopify admin, go to Settings > Checkout and look at the Configurations section. If you see an upgrade notice, open the personalized upgrade guide, which lists your existing customizations and how to recreate them.

Why Checkout Extensibility Is Better

Checkout extensibility replaces fragile code injection with an app-based architecture.

• Upgrade-safe: extensions run on Shopify's supported platform, so you get new checkout features without your customizations breaking.
• Secure and sandboxed: according to shopify.dev, checkout UI extensions run in an isolated sandbox, can't access sensitive payment information or the checkout page's HTML, and are limited to approved components and APIs.
• Built for performance: extension bundles are capped at 64 KB, and they use Shopify's own Polaris web components, so they look native and load quickly.
• Editable without code: merchants place and arrange app blocks in the checkout and accounts editor.

The three building blocks

• Checkout UI extensions: custom UI blocks in checkout and on the Thank you and Order status pages. Current versions use Polaris web components with Preact.
• Shopify Functions: backend logic for things like custom discounts, and delivery and payment customizations.
• Web pixels: sandboxed, event-based tracking that replaces scripts for analytics and ad platforms.

What needs Shopify Plus?

Checkout UI extensions in the Information, Shipping and Payment steps are available only on Shopify Plus. Extensions on the Thank you and Order status pages are available to merchants on all plans.

3 Strategies to Grow Revenue With Checkout Extensions

The strongest brands aren't just migrating, they're improving. Here are three ideas worth testing.

1. Smart in-checkout upsells

Don't wait for the Thank you page. A custom block can suggest relevant add-ons, such as gift wrapping, an extended warranty or a matching accessory, right in checkout, where the buyer already intends to purchase. On Plus you can place these in the main checkout steps. On any plan you can add post-purchase offers on the Thank you page. Measure the results with an A/B test instead of relying on industry averages.

2. Dynamic free-shipping progress bar

A progress bar that updates in real time ("You're $10 away from free shipping") gives buyers a clear reason to add one more item, especially when it sits next to a one-tap product suggestion that bridges the gap.

3. Trust-building UI

Reassurance matters most at the moment of payment. Blocks with reviews, guarantees, return-policy highlights or an estimated delivery date can reduce hesitation. Keep them honest and accurate. Shopify's own design guidance discourages pressure tactics like fake countdown timers.

Bonus: Get the address right

Many failed deliveries start with a wrong or vague address. Our own app, Addressly, holds Shopify's Built for Shopify badge and is a good example of checkout extensibility in action. On Shopify Plus it adds a native inline map card to checkout from the checkout editor, with address autocomplete (Google Maps and OpenStreetMap) and a map pin for the exact drop-off point.

How Winsomies Can Help

Migration isn't just moving code. It's a chance to redesign your checkout. Winsomies is a Shopify app studio and development partner, and we build and maintain apps on these same extension APIs. We can help with:

• Custom checkout UI extensions: branded blocks for upsells, shipping bars, trust content and custom fields, built with Polaris web components so they feel native.
• Shopify Functions development: discount logic, and delivery and payment customizations that standard apps don't cover.
• Pixel migration: moving tracking from additional scripts to web pixels and app pixels, then checking that conversions still record.
• Post-upgrade audits: finding what your old checkout.liquid or scripts did and rebuilding what still matters.

Final Thought

The deadline isn't something to dread anymore. It's behind you. The question now is whether your checkout is as good as it could be. Treat checkout extensibility as a fresh start: faster, safer and finally customizable without fear of breaking.

Is your checkout working as hard as it should? Talk to Winsomies →

Frequently Asked Questions

Is checkout.liquid still supported?

No. It's unsupported for the Information, Shipping and Payment steps, and it was sunset for the Thank you and Order status pages on August 28, 2025.

What happened to Plus stores that didn't upgrade by August 28, 2025?

Their additional scripts and checkout.liquid became read-only. From January 2026, Shopify began upgrading their Thank you and Order status pages automatically, replacing the legacy pages and their customizations.

What was the deadline for non-Plus stores?

Stores on non-Plus plans had until August 26, 2026 to upgrade and replace their Thank you and Order status pages. Script tags on those pages were sunset on that date.

What replaces Additional Scripts?

Shopify's upgrade guide points you to built-in features, apps, app blocks and web pixels. Tracking scripts should move to app pixels or custom web pixels.

Do I need Shopify Plus for checkout UI extensions?

Only for the Information, Shipping and Payment steps. Extensions on the Thank you and Order status pages are available on all plans.

What are Shopify Functions?

Functions are backend extensions that customize Shopify logic, such as discounts, and delivery and payment options, without touching checkout code.

Can Winsomies rebuild my old checkout customizations?

Yes. Winsomies builds checkout UI extensions, Shopify Functions and web pixel migrations, and can audit what your legacy checkout did and rebuild what still matters.