Post-Purchase Upsell
What is a post-purchase offer
A primer on Shopify's checkout_post_purchase API and how Oxify uses it.
This article is a draft and may be incomplete or change before publishing.
After a customer completes checkout but before they reach the thank-you page, Shopify shows a one-page offer to add another product to the existing order — same payment method, no re-entering anything. Acceptance creates a single combined order.
Why this matters
Post-purchase offers convert higher than any other upsell surface because:
- The customer has already paid — no second checkout friction.
- The price is anchored to "your order", not "a new purchase".
- One click adds the product to the existing payment.
Technical foundation
This module is built on Shopify's checkout_post_purchase extension API. The offer is rendered server-side based on the order's contents, signed at acceptance, and applied via Shopify's applyChangeset API.
What it isn't
Post-purchase ≠ thank-you page upsell. The thank-you page (Order Status) is separate — see Section 7 for that.