It's February 2026. The Shopify Checkout Extensibility deadline came and went. And if you're reading this, there's a decent chance your Shopify Plus store is still running on legacy Thank You and Order Status pages which means your tracking is probably broken, your customizations are locked, and you've got an auto upgrade email sitting in your inbox (or coming soon).

You're not alone, and the good news is that the migration is straightforward once you know what's actually changed. This isn't another "migrate now or else" scare piece. You've seen enough of those. This is the practical guide for merchants who missed the August 28, 2025 checkout.liquid deadline and need to understand what's happening to their store right now and what to do about it.

Table of Contents

• The Checkout Extensibility Timeline

• What Changed After the August 2025 Deadline

• Shopify Thank You Page Auto Upgrades (January 2026)

• Why Broken Tracking Is Costing You Money

• How to Migrate to Checkout Extensibility (Step by Step)

• Google Tag Manager and Checkout Extensibility

• What Replaces Additional Scripts, GTM, and Custom Code

• Checkout Branding and Customization After Migration

• Shopify Markets and International Checkout Considerations

• Shopify Scripts vs Checkout Extensibility (Different Deadlines)

• Post Purchase Order Editing After Checkout Extensibility Migration

• The Bottom Line

• Frequently Asked Questions

The Checkout Extensibility Timeline (The Short Version)

Shopify has been moving away from checkout.liquid for years. Now that checkout.liquid is officially deprecated, here are the milestones that matter:

• August 2024: checkout.liquid stopped working for the main checkout pages (Information, Shipping, Payment)

• August 28, 2025: The deadline for Thank You and Order Status pages on Plus stores

• January 2026: Shopify started auto upgrading stores that hadn't migrated yet

If you're still seeing an "upgrade your Thank You and Order Status pages" notice in Settings → Checkout, you're on the legacy system. And that means several things are already different for your store.

What Changed After the August 2025 Deadline

Here's the thing nobody explains clearly: the deadline wasn't just a deadline. Shopify started limiting functionality immediately after August 28, 2025 to protect checkout security. So even before any auto upgrade happens, your store is already affected.

Your Additional Scripts field is locked. You can look at it, but you can't edit it. That tracking code you wanted to tweak? The pixel you needed to update? Locked. Shopify won't let you touch it. If you've been searching "Shopify Additional Scripts not working," this is why the field is frozen and will eventually be deleted entirely.

Your tracking is missing customer data. This is the big one. On legacy Thank You and Order Status pages, Shopify stopped passing PII (email, phone, name, address) to your tracking scripts and pixels. Your Google Ads enhanced conversions? Degraded. Your Meta audience matching? Broken. Your Klaviyo purchase tracking? Missing customer identifiers. You might have noticed your ROAS looking off since late August. This is probably why.

Your checkout.liquid customizations are on borrowed time. They might still be rendering. They might not. Shopify describes it as "being shut down" which is deliberately vague. The point is: don't trust anything in checkout.liquid to keep working. It's deprecated, unsupported, and will be deleted when your store gets upgraded.

Any apps using script tags are degraded. If you have older apps that inject functionality via script tags (common for upsells, reviews, tracking), those are in the same boat. Deprecated, unreliable, going away. You'll need to replace them with apps built on Checkout UI Extensions the new standard for checkout customization.

Shopify Thank You Page Auto Upgrades (January 2026)

Here's what's happening right now: Shopify is emailing Plus stores that haven't upgraded, giving them 30 days notice, then automatically upgrading them.

When that auto upgrade happens:

• All your Additional Scripts content gets deleted

• All your checkout.liquid code gets removed

• Script tag app functionality gets disabled

• Shopify might move some of your analytics scripts to custom pixels automatically, but this is "best effort" and "limited" don't count on it

But here's the part everyone misses: after the upgrade, PII comes back. Your checkout_completed pixel events will include customer email, phone, and other data again. The upgrade actually fixes your tracking data assuming you've set up Shopify custom pixels to receive it.

So the auto upgrade isn't the disaster. The disaster is getting auto upgraded before you've rebuilt your tracking and customizations. Then you've got a gap where nothing works.

Why Broken Tracking Is Costing You Money

Let me be real about the impact. If you're running paid ads Google, Meta, TikTok, whatever your conversion tracking has been degraded since late August. Your campaigns are optimizing on incomplete data. Your audiences are missing customers. Your ROAS calculations are wrong.

A DTC apparel brand we work with saw their reported Facebook ROAS drop from 4.2x to under 1x. They thought their ads had tanked. Nope their tracking had tanked. The ads were performing fine. They just couldn't see the conversions because the Thank You page wasn't passing customer data to Meta's pixel anymore.

If you have custom Thank You page elements upsells, cross sells, review requests, loyalty program signups, custom messaging those are either already broken or about to be deleted.

If you're using Google Tag Manager in checkout, that's a whole separate headache (more on this below).

How to Migrate to Checkout Extensibility (Step by Step)

You have three paths. Only one is smart.

Path 1: Upgrade Manually Before Shopify Does It For You (Do This)

This is the move. You control the timing, you can set up your new tracking first, and you avoid the gap where nothing works.

First, confirm you're still on legacy pages:

1. Go to Settings → Checkout in your Shopify admin

2. Look in the Configurations section

3. If you see a notice about upgrading Thank You and Order Status pages, you're on legacy

Second, inventory what you're going to lose:

Open your Additional Scripts field and copy everything out. Screenshot it. Save it somewhere. Same with any checkout.liquid customizations. Make a list of every app that touches your checkout pages. You can't edit this stuff anymore, but you can document it so you know what to rebuild.

Third, set up your new tracking BEFORE you upgrade:

This is the key insight. You can install Shopify custom pixels, the Google & YouTube app, the Facebook & Instagram app all of that works alongside your legacy setup. Get it working first. Verify it's firing. Then upgrade.

For most stores, this means:

• Install the Google & YouTube app for GA4 and Google Ads conversion tracking

• Install the Facebook & Instagram app for Meta Pixel and Conversions API

• Create custom pixels in Settings → Customer Events for anything else (TikTok, Pinterest, affiliate tracking, etc.)

Under the hood, Shopify's custom pixel system uses the Web Pixel API and analytics.subscribe() to listen for checkout events like checkout_completed, payment_info_submitted, and checkout_started. If you're a developer or working with one, Shopify's Web Pixel API reference is the technical doc you'll need.

Fourth, rebuild your customizations:

Visual stuff and functionality now lives in the checkout and accounts editor, using blocks and app extensions. Upsells, messaging, branding find Checkout Extensibility compatible apps or use Shopify's native blocks.

Fifth, pull the trigger:

1. Settings → Checkout

2. Find your configuration, click "Open upgrade report"

3. Review what Shopify thinks needs attention

4. Click Upgrade

Sixth, verify everything:

Place a test order. Check every tracking platform. Make sure pixels are firing, data is flowing, PII is showing up in your events. Don't skip this step a five minute test order now saves weeks of bad data.

Path 2: Wait for Auto Upgrade (Please Don't)

You'll get a 30 day email. Then Shopify upgrades you automatically. Your legacy stuff disappears. Maybe some analytics scripts get migrated to custom pixels. Maybe not.

Meanwhile you're flying blind on conversion tracking while you scramble to set up pixels. Your ad platforms are optimizing on nothing. You have no idea what's actually converting.

Don't do this.

Path 3: You've Already Been Auto Upgraded

If Shopify already upgraded your store, your legacy code is gone. There's no undo button Shopify doesn't document a rollback path after automatic upgrades.

The good news: PII is flowing again. Set up your pixels now and you'll start getting good data immediately.

The bad news: you probably have a gap in your conversion data from the upgrade date until you get tracking working. Focus on getting pixels set up as fast as possible. The data gap is done just stop it from getting bigger.

Google Tag Manager and Checkout Extensibility

I need to address this separately because a lot of Plus merchants have invested heavily in GTM setups.

Here's the reality: GTM doesn't work the same way in Shopify's new system. Shopify Pixels run in a sandboxed environment that can't access the DOM, can't run arbitrary JavaScript, and doesn't support Tag Assistant for debugging.

If you had a sophisticated GTM container with custom HTML tags, DOM scraping, or complex triggers that won't work in Checkout Extensibility.

But Shopify does offer two paths:

1. Google & YouTube app (recommended): Handles GA4 and Google Ads natively without needing GTM at all. For most stores, this is actually simpler and works better.

2. GTM via custom pixel (limited): You can technically run GTM through a custom pixel, but with significant limitations and no Tag Assistant. Shopify's docs describe this as "not recommended" with "limited support."

If your GTM setup was mostly for Google tracking, just use the Google & YouTube app. It's easier.

If you have complex GTM implementations for other purposes, look into server side tracking solutions like Elevar, Analyzify, or Stape. They're built for this exact situation and have updated their platforms specifically for Checkout Extensibility compatibility.

What Replaces Additional Scripts, GTM, and Custom Code

Checkout Branding and Customization After Migration

One thing merchants often overlook: the new checkout editor gives you more branding control than checkout.liquid did for most use cases. After migrating, go to Settings → Checkout → Customize to access the checkout branding editor.

You can control colors and fonts across the entire checkout, add your logo with precise positioning, customize form fields, error states, and button styles, add custom banners, trust badges, and informational blocks using Thank You page and Order Status page blocks, and use app blocks from Extensibility compatible apps for dynamic content.

The editor is visual and doesn't require code, which is a genuine upgrade from editing Liquid templates. If you had a developer maintaining your checkout.liquid, they can now focus on building Checkout UI Extensions for anything the native editor doesn't cover.

Shopify Markets and International Checkout Considerations

If you're selling internationally using Shopify Markets, there are a few extra things to think about during migration.

Your checkout.liquid might have contained locale specific logic, custom address formatting for different countries, or currency display tweaks. After migration, Shopify Markets handles most of this natively but you should verify that your checkout experience still works correctly for each market you sell into.

Pay particular attention to address validation for international orders (some custom address logic may need to be rebuilt), pixel tracking for region specific ad platforms (like LINE for Japan or Naver for Korea), and any market specific checkout messaging or compliance notices you had in checkout.liquid.

Test a checkout flow for at least your top two or three international markets after upgrading. Issues with address formatting or missing compliance messages are easier to catch with a test order than with an angry customer email.

Shopify Scripts vs Checkout Extensibility (Different Deadlines)

Don't confuse this with Shopify Scripts the Ruby based tool for custom discounts, shipping rules, and payment logic. That's a separate deprecation with a separate timeline:

• Script Editor app is no longer available for new installs

• Existing Scripts stop working June 30, 2026

If you use Scripts, you'll need to migrate to Shopify Functions before then. That's a different project from Checkout Extensibility, though many merchants will end up doing both migrations in the first half of 2026.

Post Purchase Order Editing After Checkout Extensibility Migration

If your store relies on post purchase functionality letting customers edit orders, change shipping addresses, swap products, or add items after checkout you'll need apps built on Checkout UI Extensions to keep that working.

Since this is the Revize blog: Revize is fully compatible with Checkout Extensibility. It uses Checkout UI Extensions, not the deprecated script tag approach. Self-service order changes, post purchase upsells, address edits all working on the new Thank You and Order Status pages.

You'll need Extensibility compatible apps for anything you want on those pages, and Revize is one of them.

The Bottom Line

If you haven't upgraded yet:

1. This week: Check Settings → Checkout to confirm you're still on legacy

2. Next few days: Document everything in Additional Scripts and checkout.liquid

3. Before you get the 30-day email: Set up your new tracking (Google app, Meta app, custom pixels)

4. Once tracking is verified: Manually upgrade

5. After upgrade: Test everything with a real order

The deadline passed, but you can still do this right. The worst outcome is getting auto upgraded with nothing ready to replace what you lose.

One more thing: after you upgrade, your tracking actually gets better. PII comes back. Enhanced conversions work properly. The new system isn't worse it's just different. The pain is the migration, not the destination.

Good luck. You've got this.

Frequently Asked Questions

How do I know if I'm on legacy Thank You pages?

Go to Settings → Checkout. Look in the Configurations section. If there's a notice about upgrading Thank You and Order Status pages, you're on legacy. If you don't see that notice, your store has already been upgraded either manually or automatically.

Why did my tracking break after August 2025?

Shopify stopped passing PII (email, phone, etc.) to legacy scripts after the August 28 deadline. Your pixels are still firing, but they're missing the customer identifiers needed for enhanced conversions and audience matching. This is why your reported ROAS likely dropped even if your actual ad performance didn't change.

Will Shopify automatically migrate my tracking scripts?

Shopify says they'll move a "limited number" of analytics scripts to custom pixels on a "best effort basis" during auto upgrade. Translation: maybe, partially, don't count on it. Set up your own pixels before the upgrade to avoid any gaps.

Can I undo a Checkout Extensibility auto upgrade?

Shopify doesn't document a rollback path after automatic upgrades. If you manually upgrade, there's a limited revert option (only if your store was created before January 6, 2025, had pre existing customizations, and you upgraded less than 30 days ago). But after auto upgrade? No documented way back.

How long does the Checkout Extensibility migration take?

For most stores, the actual upgrade takes minutes. The real time investment is in preparation: documenting your existing scripts (1 to 2 hours), setting up new pixels and verifying they fire correctly (2 to 4 hours), and rebuilding any custom Thank You page elements with Extensibility compatible apps (varies by complexity). A straightforward store can do the full migration in a day. Stores with complex GTM setups or heavy checkout.liquid customization might need a week or more.

How do Elevar and Analyzify work with Checkout Extensibility?

They've updated for Checkout Extensibility, but you'll need their server side plans to recover checkout events. The old Data Layer approach doesn't work in the new sandbox. Check their docs for migration steps specific to your tracking setup.

Is Checkout Extensibility only for Shopify Plus?

The August 28, 2025 deadline was for Plus stores. Non Plus stores have until August 26, 2026 for the Thank You and Order Status page migration. But Shopify Pixels work for all plans you can start using them now regardless of your plan.

What's the difference between Checkout Extensibility and Shopify Scripts?

Different systems entirely. Checkout Extensibility replaces checkout.liquid and Additional Scripts for page customization and tracking. Shopify Scripts is the Ruby based tool for discounts, shipping, and payment logic that's being replaced by Shopify Functions, with a deadline of June 30, 2026.

What is the Web Pixel API?

The Web Pixel API is Shopify's replacement for the old Additional Scripts approach. It lets you subscribe to checkout events (like checkout_completed) using analytics.subscribe() and run tracking code in a sandboxed iframe. It's how custom pixels work under the hood. See Shopify's Web Pixel API docs for technical details.

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• How to Edit an Order on Shopify: Complete Guide

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• Best Shopify Customer Service Apps (Tested & Ranked)

• Shopify Checkout Customization: Complete Guide to Branding Your Checkout

Last updated: February 2026