FBT discount function

FBT discounts are applied by Oxify's unified discount function — the single Shopify Function behind the automatic discount titled Oxify Cart Unified Discount. The same function also handles volume discounts, upsell discounts, free gifts and cart reward discounts. Oxify creates and updates it for you whenever you save a product page offer; you don't create anything in Shopify admin.

Logic

At checkout, for every Active offer that has a discount, the function:

1. Finds the cart lines that were added with that offer's button.
2. On a Frequently bought together offer, checks that at least Minimum products required for discount different products are among them (the default is 2, and the editor doesn't accept less).
3. If Apply discount type is Only if trigger product is in cart, checks that the trigger product is still in the cart.
4. Takes the percentage off each of those lines, or the fixed amount off each unit of them.

Offers set to No Discount, or with a value of 0, are ignored. Items bought with a subscription are skipped while Exclude subscription products from discounts is on (the default). Fixed amounts are entered in your store currency and converted for shoppers who pay in another currency.

Status

Oxify keeps the discount up to date: saving, activating, deactivating or deleting an offer updates it. To see it, open Shopify admin → Discounts and look for Oxify Cart Unified Discount.

Migration

If your store used Oxify before the unified discount existed, the Product Page Upsell page shows an Upgrade Required panel instead of your offers. Click Migrate Now once. It replaces the old discount functions with the unified one, keeps your Cart Rewards settings, and refreshes the page when it's done. See Migrate from legacy to unified.

Combinations

Whether FBT discounts stack with your other discounts is set in Oxify, not in Shopify admin: in the cart editor, open Settings → Discount Settings and use Combine with other Order discounts, Combine with other Product discounts and Combine with other Shipping discounts (all on by default). Oxify re-applies these settings to the discount whenever it saves, so changes made to the combinations on the discount's page in Shopify admin can be overwritten.

Size limit

Shopify limits the settings a checkout discount can read to 10,000 bytes. When your active offers get close, the offer page shows an Approaching the size limit banner, and a save that would go over the limit is refused with a "Not saved" message. Remove some products or collections, or deactivate offers you no longer use, then save again.