Testing legacy "Additional Scripts" vs. Checkout Extensibility for Post-Purchase Survey

Shopify App Store
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Hi everyone,

I am developing a post-purchase survey app and I’m looking for advice on testing legacy compatibility.

We have already built and deployed a Checkout UI Extension (using React and the Shopify CLI) for merchants who have upgraded to Checkout Extensibility. That side is working perfectly.

However, we still need to support merchants on older plans or those who haven’t transitioned yet via the traditional “Additional Scripts” (Order Status Page) method. My legacy script uses Liquid tags (like {{ order.id }} and {{ order.line_items }}) to build a JSON payload and injects a <div> for the survey UI.

The Challenge: Because all new development stores default to Extensibility, I am struggling to find an environment to test the Liquid-to-JS data mapping and the DOM injection for the “old” way.

My Questions:

  1. For those supporting both modern Extensions and legacy scripts, how are you testing the “Additional Scripts” version on newer Partner stores?

  2. Is there a specific “Legacy Checkout” flag or Storefront version I can request for a Dev store to get the old checkout.liquid / Additional Scripts behavior back just for testing?

  3. Since the order object isn’t available on the PDP, is there a way to “mock” a completed order page to verify my Liquid loops ({% for line_item in order.line_items %}) are rendering the JSON correctly?

I want to ensure a seamless experience for our non-Plus or legacy merchants, even though our primary focus is the new Extension.

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Hey @Abhishek_Purohit :waving_hand: thanks for reaching out. For context, Additional Scripts have been fully deprecated as of August 28, 2025, and the Additional Scripts section is now view-only across all stores, so even if the merchant has a legacy environment, you wouldn’t be able to add new scripts to test.

For non-Plus merchants you’re hoping to support, they have until August 26, 2026 before their Thank you and Order status pages are automatically upgraded and any legacy scripts stop functioning entirely, and for Plus merchants they are within the process of auto-upgrading within the next 30 days or so. Given this timeline, I’d say that focusing your engineering effort on the Checkout UI Extension path you’ve already built is probably the best bet, since it will soon be the only option for all merchants.

You can review the full deprecation details and migration guidance here: https://help.shopify.com/en/manual/checkout-settings/customize-checkout-configurations/upgrade-thank-you-order-status/index

If you do have existing merchants currently using your legacy script, you could potentially test updates on their stores via collaborator access, but building new legacy support at this time isn’t possible. Hope this helps!

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Thanks @Alan_G for your support.

1 Like
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No worries @Abhishek_Purohit - I’ll close out the thread for now, but let me know if I can help out further :slight_smile:

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Hey @Alan_G, I have access to the store now. Regarding the implementation: can we use the theme editor to render static Liquid and handle API requests driven by user input? Looking for the best way to bridge the two on the post purchase page