Last year's checkout deadline got the headlines. This year's is the one that finishes the job, and it lands on the two pages most merchants forget they customized.
On August 28, 2025, Shopify ends support for legacy checkout.liquid customizations on the Thank You and Order Status pages. If your store still relies on the old checkout to render those two pages, this is the date the safety net is removed. The direct answer for most merchants: your products, prices, and discount logic are fine, but any post-purchase upsell, tracking block, or custom content living on the Thank You or Order Status page needs to move to checkout extensibility before the deadline, or it stops working.
This is the sequel to the deadline that hit the front of checkout last year, and it is worth understanding precisely, because the parts that break and the parts that do not are easy to confuse.
What actually changes on August 28
Shopify has spent two years moving merchants off checkout.liquid, the old editable checkout, onto checkout extensibility, a system of sandboxed UI extensions and apps. The migration happened in stages by page.
The August 13, 2024 deadline covered the information, shipping, and payment steps, the pages where customers enter details and pay. August 28, 2025 covers the last two pages in the flow: the Thank You page a customer sees immediately after paying, and the Order Status page they return to for tracking and updates.
After the deadline, customizations on those two pages that depend on legacy checkout.liquid are no longer supported. They can quietly fall back to a default experience, which is the trap: nothing throws an error, the page just stops doing the extra thing you built.
What breaks, and what does not
It helps to separate the layers.
| Layer | Affected by Aug 28? | Why |
|---|---|---|
| Discount and pricing logic on Shopify Functions | No | Functions run in the discount engine, not the checkout page |
| Volume, shipping, and Buy X Get Y discounts | No | Applied server-side before the customer reaches these pages |
| Post-purchase upsell on the Thank You page | Yes | Rendered in the checkout page layer being deprecated |
| Custom content or scripts on Order Status | Yes | Injected through legacy checkout.liquid |
| Analytics or tracking pixels in checkout.liquid | Yes | Depend on the old editable checkout |
The pattern: anything that computes a price is safe, because that work happens in Shopify Functions long before these pages render. Anything that draws something onto the Thank You or Order Status page through the old checkout is what needs attention.
This is exactly why building discount logic on Functions has aged well. If your volume discounts or free shipping thresholds run through the native engine, they were never touching checkout.liquid in the first place, and this deadline passes over them entirely.
Why the Thank You page is the sneaky one
The Order Status page is a known quantity: most merchants know they added a tracking widget or a support link there. The Thank You page is where the surprises live, because it is prime real estate for post-purchase offers and merchants often installed those through apps or snippets they have long forgotten.
A post-purchase upsell that appears right after payment is one of the highest-converting placements in ecommerce, precisely because the customer has already committed. If yours is built on the legacy checkout, it is on the list. The customer will still complete their order, they just will not see the offer, and you will not get an error telling you why revenue dipped.
A migration checklist for discount merchants
You do not need to rebuild your checkout. You need to inventory two pages and move what lives on them.
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List every customization on the Thank You and Order Status pages. Post-purchase upsells, order tracking widgets, custom messaging, referral prompts, survey blocks, tracking pixels. Write them down before you touch anything.
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Sort each one into "moves" or "already fine." Anything running through an app that supports checkout extensibility is likely already migrated by the vendor. Anything you added by editing
checkout.liquidor through a snippet needs to move. -
Check your apps' status. Open each app that touches post-purchase or order status and confirm it supports checkout extensibility. Reputable vendors have shipped their migration already; ask the ones that have not.
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Rebuild upsells as checkout UI extensions. Post-purchase offers move to the extension model. If your current upsell tool is not migrating, this is the moment to switch to one that has.
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Confirm your discount logic is untouched. Verify that your pricing runs on Shopify Functions, not on anything in the checkout page layer. If it does, you can leave it alone with confidence.
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Test the full flow after migrating. Place a real test order and walk through payment, Thank You, and Order Status. Confirm every widget you kept still renders and every discount still applies at the right price.
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Do it before the last week of August. Peak BFCM prep is weeks away. You do not want to be debugging your Thank You page in October.
The bigger direction this points to
Zoom out and the two checkout deadlines tell one story: Shopify is consolidating checkout into a sandboxed, upgrade-safe model where merchants customize through defined extension points rather than by editing a template. The upside is that once you migrate, future checkout upgrades stop breaking your customizations. The cost is this one round of migration work.
It also rhymes with the wider platform direction we wrote about in the Summer '25 Editions recap: logic belongs in defined, native surfaces, not in patched templates. Discounting made that move years ago with Functions. Checkout is finishing the same journey now.
If your pricing is already Functions-native, August 28 is a small chore about two pages, not a fire. Inventory them, move the upsells, test the flow, and get back to preparing for the season that actually matters.
