What is a post-purchase offer
A primer on Shopify's checkout_post_purchase API and how Oxify uses it.
After a customer completes checkout but before they reach the thank-you page, Shopify shows a full-page offer to add another product to the existing order — same payment method, no re-entering anything. Acceptance adds the product to the existing order, so there is still just one order. Oxify can chain up to three offers one after another.
Offers only show once Oxify Post Purchase is selected under Post-purchase page in your Shopify checkout settings. The Post Purchase page in the Oxify app warns you if it isn't.
Why this matters
Post-purchase offers are easy for buyers to accept 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. When the buyer reaches the post-purchase step, Oxify picks the matching funnel and prepares the offer from the order's contents. When the buyer accepts, Oxify signs the change and Shopify applies it to the existing order (applyChangeset).
What it isn't
Post-purchase ≠ thank-you page upsell. Upsells on the thank-you page and the order status page are a separate feature — Thank You & Order Status in the Oxify app (see "Order Status Upsell (OTO) — concept").