This article is the single reference for diagnosing and resolving Gift With Purchase (GWP) and discounting problems in Rebuy. It covers how the discounting system works, a diagnostic checklist for where to start, the most common merchant-reported issues with their causes and fixes, a reference for specific error messages, debugging tools, what is and is not supported, and Shopify platform constraints that affect every Rebuy merchant.

Several Rebuy GWP and discounting features share the same underlying prerequisites. Rather than restate them in every section, confirm the following foundational items first — most 'it's not working' cases resolve back to one of these:

Each Rebuy widget that applies a discount has its own Shopify Functions toggle (or, in Bundle Builder's case, a dropdown). If Rebuy Discounting is being used on a widget, "Discounted By Functions" — or that widget's equivalent setting — must be enabled. This setting is one of the most frequently missed configurations, and the toggle is intentionally off by default on most widgets. If discounts are not applying as expected on a specific widget, this is the first place to check on that widget specifically.

The exact path and setting name varies by widget:

Rebuy's discounting system runs on Shopify Functions. Every discount Rebuy applies to a cart is a Shopify Automatic Discount that Rebuy creates and manages behind the scenes. There are exactly two of these in the Shopify Admin for any Rebuy store:

Each Rebuy discount is scoped by widget ID and line item attribution. When a customer adds a product through a Rebuy widget, Rebuy writes attribution properties onto that line item; the Shopify Function then reads those properties at cart and checkout and applies the discount only to items that carry the attribution.

Understanding this architecture explains most of the issues in this article. A discount that "is not applying" almost always means one of three things: the attribution did not get written, the Shopify Functions toggle is off, or the Rebuy-managed Automatic Discount in Shopify has been paused, expired, or overridden by a non-combinable discount.

Rebuy evaluates each product's Shopify lifecycle status at datasource query time. The status set on the gift product in Shopify Admin directly determines whether Rebuy can return it through a widget — including for Gift With Purchase setups.

Why this matters for GWP setups. Shopify's Unlisted status is the cleanest native way to keep a gift product out of collections, storefront search, internet search, and Rebuy AI/recommendation surfaces — without any tags or metafield workarounds. The gift remains available to Rebuy when explicitly pinned in a GWP widget's datasource via a Specific Product return, and is invisible everywhere else. For most GWP setups, Unlisted has replaced older "hidden product" workarounds (such as the seo.hidden metafield and exclude_rebuy tag) — those are only needed for products that must remain Active. See the live Help Center article "Using Unlisted Products for Gift with Purchase Offers" for full setup, including the $0 pricing trade-off.

Setup path for Unlisted gift products: Shopify Admin → Products → [gift product] → Status → Unlisted → Publish to Online Store sales channel → Save. The product must remain published to the Online Store channel even when Unlisted (Unlisted controls discoverability, not channel availability). Without that, Rebuy cannot return it.

Datasource configuration for Unlisted gifts: in the GWP widget's datasource, the RETURN must be set to Specific Product with the Unlisted gift explicitly chosen. AI, Top Sellers, collection, tag-based, and algorithmically-ranked returns will never surface an Unlisted product, regardless of other configuration.

Rebuy's GWP validation logic (sometimes referred to as the GWP watcher — the two names refer to the same feature and are used interchangeably in Rebuy documentation and support) can run actively during the Shopify checkout process. When active, it monitors cart changes at checkout and re-evaluates the GWP widget's datasource rules to ensure that any gift items in the cart remain valid. If a customer removes qualifying items and no longer meets the gift conditions — or a discount code applied at checkout drops the subtotal below the threshold — the watcher automatically removes the gift from checkout.

This section covers how checkout GWP validation works, what requirements apply, how the automatic gift removal behaves at checkout, and a newer setting — Treat as Gift With Purchase — that extends this behavior to checkout offer (recommendation) widgets.

Shopify Plus only. All GWP validation at checkout requires Shopify Plus. This feature depends on Shopify checkout extensions, which are exclusive to Shopify Plus plans. Non-Plus stores cannot access this feature at all.

For the GWP validation logic to run at checkout, all four of the following must be true:

When a customer proceeds to checkout, the GWP watcher checks two things about every GWP item in the cart: (1) is the widget's datasource still valid (does the cart still satisfy the rules, and does the datasource resolve to a deterministic set of specific products), and (2) is there an active Rebuy discount still applied to the gift line item. The watcher then decides whether to keep or remove the gift based on the combination:

Note: The auto-removal at checkout applies only at the checkout step itself. If a customer navigates back to the cart, the gift item may still be present there. Auto-removal also does not apply to gifts added through the Tiered Progress Bar — customers can remove those directly from the progress bar themselves, and TPB gifts follow the separate Checkout Extensions Tiered Progress Bar path.

Checkout offer (recommendation) widgets now include a Treat as Gift With Purchase setting in their Advanced Settings tab. When this setting is enabled, items added by that checkout offer widget are treated by the same GWP watcher as standard GWP items — meaning cart conditions are validated and the gift is automatically removed if those conditions are no longer met, exactly as it would be for a standard Gift With Purchase Widget.

This is useful for any Shopify Plus merchant using a checkout recommendation widget to deliver a GWP offer at checkout rather than a standard GWP widget.

To enable this setting:

Important dependency: If Enable Attribution Tracking is toggled off after Treat as Gift With Purchase has been enabled, the Treat as Gift With Purchase setting automatically turns off as well and cannot be re-enabled until attribution tracking is turned back on. These two settings are dependent on each other.

Once enabled, the checkout offer widget operates under the same GWP watcher validation as a standard GWP widget. All requirements and limitations in this section apply — Shopify Plus is required, at least one checkout widget must be active on the checkout page, and unsupported rule types (URL rules, order tag rules) are skipped.

There are four known limitations to GWP validation at checkout:

When a store uses Shopify Markets with fixed market prices (rather than dynamic currency conversion), the GWP watcher may incorrectly remove gifts at checkout for customers shopping in a non-default currency. Shopify does not expose currency conversion rates at checkout, which causes the watcher's threshold calculations to use incorrect values.

Problem scenario (different currency + fixed pricing):

Workaround: if the store uses Shopify Markets with fixed pricing across multiple currencies, test GWP threshold behavior in each currency where fixed prices are in use. Consider setting thresholds that account for the discrepancy, or switch to dynamic (non-fixed) pricing on the products involved in GWP promotions.

Before diving into a specific symptom, work through this 5-step diagnostic. Roughly 80% of Rebuy Gift With Purchase (GWP) and discounting issues resolve somewhere in these five steps.

If all five checks pass and the issue is still present, move to the specific symptom below.

Note on cache propagation and published changes. When you save a change to a widget, datasource, or Smart Cart configuration, the change is usually visible immediately in the Rebuy Admin but may take a short period to reflect on the live storefront and in active customer carts. Rebuy's cart.js stores session-level data (such as GWP state and cart attribution) on existing customer sessions. This does not affect how quickly your own configuration changes appear: Smart Cart template, CSS, settings, and datasource changes should be visible immediately in a fresh incognito browser session. Shopify's CDN may also serve cached theme assets for a few minutes after a theme update. Before reporting that a change did not take effect, always test in a fresh incognito window rather than an existing browser session.

A Gift With Purchase item that flashes in and out of the Rebuy cart is almost always caused by one of two things.

Cause 1: Wrong datasource rule type. When the datasource rule is set to Equals instead of Contains Any, the rule evaluation can toggle between match and no-match as the cart updates, causing the gift to appear and disappear in a loop. Fix: open the GWP widget → Data Source → change the rule from Equals to Contains Any.

Cause 2: Cart caching. If a widget was recently modified or disabled, stale cached data can cause ghost gifts to appear. Fix: when deactivating a GWP, also set the widget's Shopify Functions discount to None (not just toggling the widget off), and always test in a fresh incognito browser session.

If a Rebuy Gift With Purchase product is not showing up in the cart when you expect it to, work through these checks in order:

If the same Rebuy gift is being added twice, the cause is almost always one of two things.

Cause 1: Datasource rule misconfiguration. Overlapping rules — for example, two rules that both return the same gift under overlapping cart states — cause a double-add. Review the rules and consolidate.

Cause 2: Third-party app conflict. Another discount or upsell app (for example, Kaching, Discount Ninja, or a competitor GWP app) is adding the same gift. Audit your installed apps for overlap.

Recommended fix: disable the Product Form Redirect setting in the Smart Cart. When Product Form Redirect is enabled, the Smart Cart intercepts add-to-cart events from the theme, which can cause Rebuy to create a second, duplicate add event. Disabling it hands add-to-cart handling back to the Shopify theme and usually resolves the duplicate-gift issue on its own.

How to disable it:

A few safeguards to apply when making this change:

Symptom: You've built a tiered Gift With Purchase using the Gift With Purchase Widget — a single datasource with multiple cart subtotal threshold rules, each returning a different, unique gift product per tier (for example: 1 free product at $50, 1 different free product at $100, 2 more different free products at $150, another different free product at $200). When the cart crosses into a higher tier (say, reaches $150), the lower-tier gift products that were previously free at the $50 and $100 tiers get re-added to the cart at full price alongside the new higher-tier gifts.

Important scope clarifications.

Cause. The datasource's rules don't have "Exit If Matched" enabled. When the cart is at $150, it satisfies the $50+, $100+, AND $150+ rules simultaneously — every threshold condition evaluates true at the same time. Without "Exit If Matched," the datasource fires every matching rule and returns the gift products from each. The previous-tier gifts get added back to the cart, but because they weren't matched through a single qualifying path with attribution carried correctly, the Rebuy Shopify Functions discount does not apply to those re-added lines — so they appear at full price.

Fix. Enable "Exit If Matched" on each rule in the datasource so that only the first matching rule fires and returns its products.

Path: Rebuy Admin → Data Sources → [GWP datasource] → open each rule → enable the "Exit If Matched" toggle → Save.

Order the rules from highest threshold to lowest so the highest qualifying tier matches first and the datasource exits at that point. With "Exit If Matched" enabled and rules ordered top-down by descending threshold, the customer only ever receives the gifts for the highest tier they currently qualify for — no cascading from lower tiers, no full-price re-adds.

If the Selectable Gift With Purchase popup is not showing, this is almost always an installation issue. Verify all four of the following:

If the Selectable GWP popup is appearing on every page load rather than only at the intended qualifying moment, the datasource trigger rule is too broad. Fix: add a cart item count condition (for example, Cart Items Count > 0) to the datasource rule so the popup only fires when the cart actually contains qualifying items — not on every homepage or PDP load.

If a Rebuy Gift With Purchase product is being added to the cart but the customer is being charged full price at Shopify checkout, the Rebuy Shopify Functions discount is not actually being applied. Work through the causes below in order.

Cause 1: Shopify Functions discount is not enabled on the widget. Go to the GWP widget → Discount tab → toggle Discounted By Functions on. For other widget types, the path and setting name differ, and each one is listed under Shopify Functions discount enablement (per widget) in the Prerequisites at a Glance section of this article. Without this, Rebuy adds the product but does not apply the $0 discount.

Cause 2: Rebuy Product Discount is inactive in Shopify. Go to Shopify Admin → Discounts. Confirm Rebuy Product Discount exists and is in Active status. If expired, paused, or missing, the discount cannot fire.

Cause 3: Widget was created before the discount was configured (widget-before-discount trap). If the GWP widget was launched before its Shopify Functions discount was configured, the widget attribution works but the discount may never fire correctly. Fix: toggle the Shopify Functions discount off and on in the widget, or recreate the discount. Future widget work should always configure the discount before enabling the widget.

Cause 4: A third-party app is conflicting with Rebuy's discounting. Some third-party apps install their own Discount API that takes precedence over Rebuy's Shopify Functions discount, which blocks the $0 gift discount from applying. A common example is the FastBundle app, since FastBundle's Discount API overrides Rebuy's discount feature and the Rebuy Smart Cart does not integrate with FastBundle. Fix: audit installed apps for any tool that manages discounts through its own Discount API, and either disable the conflicting app or choose one discounting tool per promotion. If the third-party app is essential to your setup, the GWP will need to be delivered through that app instead of Rebuy.

Cause 5: The Rebuy discount metafield that stores the gift is over Shopify's 10 KB limit. Rebuy stores Gift With Purchase widget discounts in the product-discount-widget metafield and Smart Cart Tiered Progress Bar free gifts in the product-discount-tpb metafield, and Shopify Functions stop reading a metafield above 10,000 bytes. When that metafield is over the limit, the $0 gift discount stops applying with no error in Shopify or at checkout. Fix: go to Settings > Discount Functions Storage in the Rebuy admin and check that metafield's card. If it is over the limit, turn off the Discount section on widgets you no longer use or delete unused Smart Carts until it is back under 10 KB. Full steps are in [Discount Functions Storage: Keep Rebuy Discounts Under Shopify's 10 KB Limit](LINK_NEEDED: new SUPPORT-276 article URL).

If the Gift With Purchase is firing when it should not, or not firing when it should, the cause is almost always inside the datasource rules themselves. Work through these checks:

Two concept-level points that regularly come up are worth restating on their own

The Discount Product and Discount Widget return rules inside a Rebuy datasource do not apply an actual checkout discount. They affect widget display only — the actual discount is always scoped to the widget's attribution and is applied by the Shopify Function, not by the datasource branch. If you expect the datasource rule itself to apply a discount, that expectation is wrong.

That said, the Discount Product and Discount Widget rules can be used intentionally as visual-only incentives. They will display the discounted price or incentive messaging inside the widget so the customer sees a promo — but for the actual discount to apply at checkout, the rule must be paired with a manually created automatic discount in Shopify that covers the same products or conditions. In that pairing, the Rebuy datasource rule handles the visual incentive inside the widget, and the manually created Shopify discount does the real discounting at checkout.

If you only need the actual discount to apply (not a separate visual), enable the widget-level Shopify Functions discount instead — it handles both the display and the checkout discount in one setting.

How a discount code interacts with a Gift With Purchase (GWP) or Tiered Progress Bar (TPB) threshold depends on where the customer enters the code and whether the Storefront API is enabled in the Smart Cart.

Code applied in the Smart Cart's discount code box with Storefront API enabled (recommended setup). Discount codes are validated in real time inside the Smart Cart. If applying the code drops the cart subtotal below the GWP or TPB threshold, the gift is automatically removed from the cart. Multiple discount codes can also be stacked in this mode. This is the current, fully supported behavior and the reason Rebuy strongly recommends enabling the Storefront API.

Code applied in the Smart Cart's discount code box with Storefront API disabled (legacy/deprecated behavior). Discount calculation is deferred to Shopify's checkout, so products that no longer qualify for the gift are not automatically removed from the Smart Cart. Fix: enable the Storefront API in the Smart Cart's discount-input configuration (latest Smart Cart version only). See the live Help Center article "Smart Cart: Discount Codes and Storefront API Integration" for the full setup.

Code applied at Shopify's checkout page (not in the Smart Cart). Behavior at this stage depends on which widget the gift came from — the Tiered Progress Bar or the Gift With Purchase Widget. The two follow different auto-removal paths.

For Tiered Progress Bar (TPB) gifts: Behavior depends on whether you have the Checkout Extensions Tiered Progress Bar enabled. This is a Shopify Plus–only feature (it requires access to the Shopify checkout editor, which is gated to Shopify Plus) and also requires the latest Smart Cart version. Non-Plus stores cannot access it at all.

For Gift With Purchase (GWP) Widget gifts: Rebuy has a separate GWP watcher (GWP validation logic) that runs during Shopify checkout (a different mechanism than the TPB flow above). It monitors cart changes at checkout, re-evaluates the widget's datasource rules, and auto-removes any gift items that are no longer valid — for example, when a customer removes the qualifying product at checkout, or when a discount code drops the cart below the GWP threshold or overrides the gift's free status.

Important distinction: this is not a GWP Widget rendering on the checkout page. No GWP widget displays at checkout. The validation logic simply runs in the background. Only Rebuy Checkout Extension widgets (checkout recommendations, checkout progress bar, checkout content block) can be physically installed on the Shopify checkout page.

Requirements for the GWP watcher to run at checkout:

Extends to checkout offer widgets via Treat as Gift With Purchase. Checkout offer (recommendation) widgets include a Treat as Gift With Purchase setting in their Advanced Settings tab. When enabled, items added by that checkout offer widget are validated by the same GWP watcher and auto-removed under the same conditions. Requires Enable Attribution Tracking to also be on (the two settings are dependent). See the GWP Validation at Checkout section near the top of this article for the full setup and edge cases.

Limitations of the GWP watcher's checkout auto-removal:

Smart Flow/Smart Link caveat: If a Smart Flow or Smart Link sends the customer straight from PDP to Shopify checkout (bypassing the Smart Cart entirely), Rebuy's progress-based discounts will not apply — the cart never passes through the Smart Cart layer where the GWP/TPB logic lives.

Display note: The Tiered Progress Bar's "amount remaining" visual uses Shopify's native cart subtotal, which excludes discount codes. The displayed bar may not visually move backward when a code is applied, even though the gift itself is correctly auto-removed by the Storefront API's real-time validation.

Symptom: A discount code is applied in the Smart Cart, the cart subtotal drops below the Tiered Progress Bar's unlock threshold, but the TPB continues to display as completed and the gift tier remains unlocked.

This is almost always caused by the "Exclude Discounts from Subtotal" setting being enabled in the Tiered Progress Bar's Advanced Bar Settings. When this setting is on, the TPB calculates against the pre-discount subtotal and ignores discount codes entirely — so even when a code drops the cart below the threshold, the bar stays completed and the gift tier remains unlocked.

Fix: Disable "Exclude Discounts from Subtotal" in the TPB's Advanced Bar Settings.

Path: Smart Cart Settings → Tiered Progress Bar → Advanced Bar Settings → disable Exclude Discounts from Subtotal → Save.

Note: The "Exclude Discounts from Subtotal" setting is only intended for stores running legacy Shopify Scripts configurations. If the store is not using legacy Shopify Scripts, this setting should be off.

Symptom: You have the TPB Decorative Tier paired with a Selectable Gift With Purchase Widget. When a customer applies a discount code inside the Smart Cart and drops the subtotal below the threshold, the gift is auto-removed correctly. But when the same code is applied at Shopify's checkout page instead, only the discount falls off the gift line item — the gift product itself remains in the cart, and the customer is charged full price if they proceed without noticing.

This is a limitation of the Decorative Tier + Selectable GWP Widget configuration. The Selectable GWP Widget has no visibility into discount-code changes made at the Shopify checkout layer, so it cannot detect that the cart no longer qualifies and cannot auto-remove the gift. The Rebuy Shopify Functions discount drops off the line as expected, but the gift product itself stays put. This is specific to Selectable GWP Widget — the Selectable GWP configuration does not support checkout-level auto-removal regardless of any other settings.

How to fully resolve gift auto-removal at checkout (Shopify Plus required). Two changes are needed together:

Setup path: Rebuy Admin → Checkout Extensions → Progress Bar widget → configure → paste the Widget ID into the Shopify Checkout Editor as a Rebuy Smart Component block. See the live Help Center article "Using the Checkout Extensions Shipping Tiered Progress Bar" for the full walkthrough.

Shopify Plus required. The Checkout Extensions Tiered Progress Bar depends on Shopify checkout extensibility, which is only available on Shopify Plus plans. Non-Plus stores cannot access this option.

Trade-off to be aware of. Switching from a Decorative Tier + Selectable GWP Widget to a Product Tier means customers no longer choose their gift — the Product Tier auto-adds a specific gift product when the threshold is met. If gift selection is an important part of the promotion, the Decorative Tier + Selectable GWP Widget is the setup that supports it, but checkout-level auto-removal will not be available with that configuration. You'll need to choose between customer-selectable gifts (no checkout auto-removal) or checkout auto-removal (no customer-selectable gift).

The Gift With Purchase (GWP) Widget is designed to automatically add gifts when its datasource rules match (for example, "cart subtotal ≥ $X") and automatically remove them when the rules no longer match (subtotal drops below the threshold). The catch: auto-add and auto-remove only fire where the GWP Widget is actually rendered and running.

Where the GWP Widget works correctly: product pages, PDP, the Smart Cart drawer, and any other surface where the GWP Widget is embedded and loaded. Add and remove both behave as expected on these surfaces.

Where it breaks — Shopify's native Cart Page and Shopify Checkout. Rebuy widgets do not run on these pages, so the GWP Widget's auto-remove logic has nowhere to execute. The result:

Solution 1 — Disable the Shopify native Cart Page so customers never bypass the Smart Cart. This is the cleanest fix in most setups. With "Use Cart Page" disabled, any attempt to navigate to the full cart page redirects the customer to the homepage and auto-opens the Smart Cart drawer instead. Path: Smart Carts → [Your Cart] → Global Settings (gear icon) → disable "Use Cart Page."

Solution 2 — Enable the GWP watcher (GWP validation logic) at checkout to cover the Shopify Checkout case. This lets Rebuy re-evaluate the GWP widget's datasource rules during checkout and auto-remove invalid gift items. Requirements:

See the GWP Validation at Checkout section near the top of this article for the full explainer, including the Shopify Markets + fixed pricing edge case.

Even when running, the checkout validation only removes the gift at the checkout layer — if the customer returns to the Smart Cart or native cart, the gift may still appear. This is why Solution 1 (disabling the Cart Page) is recommended in combination whenever possible.

When a customer manually removes a Rebuy gift, Rebuy stores that removal preference in a browser cookie and intentionally will not re-add the gift — even if the customer re-qualifies during the same session. This is the designed behavior of the Allow Customer to Remove Gift setting.

To override, either:

When a GWP widget is disabled, existing customer carts that already contain the gift will keep it until those carts are abandoned or cleared. This is expected behavior — Rebuy does not retroactively modify active customer carts when a widget is turned off.

To minimize the persistence window, set the GWP widget's Shopify Functions discount to None before disabling the widget (not just toggling the widget off). This clears the cache trigger and reduces how long the gift persists in active carts. Customers who already received the gift before the widget was disabled can still complete checkout with it — this is unavoidable given Shopify's cart storage behavior.

Symptom: Rebuy discounts have stopped applying to every Rebuy widget across the entire store at once, not just one widget.

If Rebuy discounts stop applying to any widget across the entire store, the first thing to check is whether the Rebuy-managed Automatic Discount was accidentally paused or deactivated in Shopify. Go to Shopify Admin → Discounts, locate Rebuy Product Discount and Rebuy Order Discount, and reactivate either that is not Active.

This is distinct from the widget-level Shopify Functions toggle. The Admin-level Automatic Discount is the parent and the widget's Functions toggle is the child. Both must be on for discounts to apply.

Important — do not disable or expire Rebuy discounts in Shopify Admin. The Rebuy Product Discount and Rebuy Order Discount entries in Shopify Admin → Discounts are the backbone of Rebuy's Shopify Functions integration. Disabling either, or setting either to "Expired," turns off all Rebuy discount functionality across the entire store — not just one widget. If this has already happened, the fix is to re-enable the discount in Shopify Admin and then clear the Smart Cart and Shopify function caches so the discount logic re-binds.

If you need to stop a specific Rebuy discount, do it at the widget level, not in Shopify Admin. Disable the Shopify Functions toggle inside the individual Rebuy widget's settings (GWP Widget, Tiered Progress Bar, etc.). This scopes the change to just that widget and leaves the global Rebuy discount integration intact.

Symptom: A Rebuy discount is no longer applying when another Shopify discount is active in the cart, or only one of the two discounts applies when both should stack.

Rebuy's Shopify Functions discounts are set to combine with all other discounts by default. However, your own manually-created Shopify discounts must also be set to combinable for stacking to work. If another store discount is not combinable, Shopify will choose one and override the other — and Rebuy cannot force Shopify to combine discounts that Shopify has not been configured to combine.

Fix: in Shopify Admin → Discounts, open every active discount and enable the Combines with other product discounts and Combines with order discounts options as appropriate.

Before assuming the combinable flag is the problem, check whether both discounts are product discounts targeting the same product, because that pairing behaves differently by Shopify plan. On Shopify Plus, two product discounts can apply to the same product once each one carries a tag the other allows. On every other Shopify plan, Shopify applies one product discount per product and keeps the larger one, no matter how the combinable settings are set.

Marking a product discount as combinable lets it stack with product discounts targeting different products, and it does not by itself place two product discounts on the same product on any plan.

On Shopify Plus, to make a Rebuy product discount and one of your own product discounts both apply to the same product, turn on Enable discount stacking under Settings > Discount Combinations in the Rebuy admin, then tag that Shopify discount rebuy and set its Product discounts combination to Multiple per product allowing rebuy. Tag only the discounts you actually want stacking with Rebuy, since a free gift discounted 100% by Rebuy will also stack with a tagged store discount on that gift's line. Full steps are in Discount Combinations: Stack a Rebuy Discount and a Shopify Discount on the Same Product.

If your store is not on Shopify Plus, the fix is not a combinable-flag change, it is to restructure the promotion so only one product discount targets any given product at a time. You can convert one side to an order-level discount, which combines with a product discount on any plan, narrow one discount's product scope so the two do not overlap, or consolidate the two promotions into a single Rebuy Functions discount with the combined logic.

Symptom: A new Rebuy discount is not generating when a widget is saved, or the Rebuy Admin surfaces a discount-limit warning.

Shopify caps active automatic function-based discounts at 25 per store. Rebuy's Functions-based discounts count toward this total. If a store is at or near the cap, new Rebuy discounts may not generate correctly, and the Rebuy Admin will show a warning.

Fix: audit and deactivate unused automatic discounts in Shopify Admin to get under 25. Rebuy recommends keeping active widget discount rules under 20 per datasource for performance, and keeping the total active automatic function discounts under 25 store-wide as a platform requirement.

If a customer removes the qualifying product and immediately clicks checkout, the gift and its discount can carry through because the cart has not had time to refresh. This is a known edge case of Rebuy's attribution-based discounting and is a Shopify-level timing issue, not a Rebuy bug.

The fix depends on which tool is delivering the gift:

Without one of these, there is no way to guarantee the discount is removed in this rapid-action scenario.

If a customer adds a product via a Rebuy widget with a discount applied, then clicks "Switch to Subscription" on that line item, the widget discount persists on the subscription variant. The Rebuy Shopify Function only checks widget-ID attribution on the line item and has no awareness of the Switch-to-Subscription event.

Workaround: hide the Switch to Subscription button via CSS on cart items that carry Rebuy widget attribution. This is a CSS-only fix, not a Rebuy-side fix — Rebuy cannot detect this event at the discounting layer.

When Rebuy discounts stop applying at Shopify checkout but look correct in the Smart Cart, a third-party discount app is often overriding Rebuy's discount at the checkout layer. Apps commonly involved: Kaching, Discount Ninja, FastBundle, and similar checkout-discounting or Discount API–based apps. FastBundle is a particularly common culprit because its Discount API blocks Rebuy's Shopify Functions discount from applying — only one discount tool can own the promotion in that pairing.

Fix: audit the installed apps for any tool that manages discounts through its own Discount API and confirm combinable settings across all discount-producing apps. If the third-party app does not support combinable discounts at all (FastBundle's Discount API is one example), only one of the two discounts will apply and you'll need to choose which tool owns that promotion — either disable the conflicting app or turn off Rebuy's Shopify Functions discount on the affected widget.

Symptom: Gifts are being double-triggered, duplicated, or the discount is behaving inconsistently when both a GWP Widget and a Tiered Progress Bar are configured against the same promotion.

Running both the Gift With Purchase widget and the Tiered Progress Bar (TPB) against the same promotion at the same time can cause double-triggering of gifts and inconsistent discount behavior.

Best practice: use one tool per promotion. If running a spend-threshold GWP, configure it either in the GWP widget or in the Tiered Progress Bar — not both simultaneously. If a visual progress indicator is needed alongside a GWP, use the Tiered Progress Bar's Decorative tier type (which provides the visual indicator only) paired with a separate GWP widget that handles the actual discount logic.

This is an important scope-and-expectation gap worth flagging up front: the Included Gift With Purchase feature in Bundle Builder applies its discount through Shopify Functions, but it does not include the GWP watcher (GWP validation logic) that the standard Gift With Purchase Widget, Selectable GWP Widget, and Checkout Extensions (with Treat as Gift With Purchase) use. That means Bundle Builder GWP gifts do not auto-add or auto-remove based on cart conditions after the customer leaves the Bundle Builder page.

What actually happens when conditions change: the gift product stays in the cart, but the Shopify Functions discount tied to the bundle falls off the line item. The customer sees the gift in the cart at full price, and if they check out without noticing, they are charged full price for a product they expected to be free (or partially discounted).

Why: Bundle Builder's gift flow is built around the bundle-tier logic on the Bundle Builder page itself, not a continuous cart-state watcher. Rebuy's GWP watcher only runs for widgets that carry GWP-widget attribution — Bundle Builder gift items do not, so the watcher never evaluates them.

Recommended fixes / alternatives:

When you build a multi-tier BXGY promotion in Smart Flows (for example: spend $100 to unlock Gift A, spend $200 to unlock Gifts A and B) and all of the selection modals fire at the same time, the cause is almost always that the tiers are stacked vertically in the flow.

Fix: rebuild the flow horizontally. In Smart Flows, build multi-tier BXGY offers as horizontal branches so each tier triggers its own modal in sequence as the customer crosses each threshold. Vertical multi-tier builds intentionally fire every downstream modal at once — that is not a bug, it is how the flow structure resolves. If the customer should see one modal per tier as they unlock it, the branches have to be horizontal.

If a Smart Flows BXGY gift product has multiple variants (for example, size or color), the variant selection modal will always appear to the customer before the gift is added. There is currently no setting to bypass or skip variant selection for BXGY gifts.

Workarounds: if variant selection must be avoided, either (a) use a gift product with only a single variant, (b) create a dedicated gift-only SKU with no variant options, or (c) switch to a standard Gift With Purchase Widget or Selectable Gift With Purchase Widget, which handle variant behavior differently. Smart Flows BXGY is not the right tool when silent variant selection is a requirement.

Symptom: A gift product priced at $0 in Shopify is being added to customer carts directly from the product page (PDP) — bypassing the Rebuy GWP widget entirely. Rebuy's discount attribution only applies to items added through the widget, not items added from the PDP, so customers can add unlimited copies for free.

There are two supported fixes, plus a Shopify Plus limitation to be aware of:

Unlisted + $0 limitation: Unlisted does not eliminate the exploit risk completely. The product page remains accessible via direct URL even when Unlisted, so determined customers who find the URL can still add the $0 product to their cart from the PDP. Depending on the store's theme, app stack, and sitemap configuration, the URL may also surface in unexpected places. To reduce (not eliminate) this risk, follow the live Help Center article "Remove the Add to Cart Button on the Product Page" to strip the buy button on the gift's PDP. For a fully robust fix, use the recommended option above (real price + Shopify Functions discount).

Unlisted + $0 limitation: incompatible with the GWP watcher at checkout (Shopify Plus only). Rebuy's GWP validation logic at checkout (the GWP watcher) requires that an active Rebuy discount be applied to the gift line item before allowing it through. A $0 Unlisted gift has no Rebuy Functions discount on the line — by design, since no discount is needed to make a $0 product free — so the watcher sees no discount and auto-removes the gift at checkout. Shopify Plus stores that need the GWP watcher should use a real-priced gift with a Shopify Functions discount instead.

Why $0 Unlisted still has a use case. Stores running stacked promotions, seasonal sale discounts, loyalty discounts, or third-party Discount API apps can run into Shopify constraints that block a Rebuy Functions discount from applying — Shopify's same-product discount rule, the 25-automatic-discount cap, or third-party Discount API conflicts. The $0 Unlisted approach removes the need for a Rebuy Functions discount entirely (no Function consumed, no combinability conflict possible), at the cost of the GWP watcher compatibility called out above. Treat it as an intentional trade-off, not a default.

Cause: A discount code that was applied in the Smart Cart was later deactivated or expired in Shopify, but remains cached in the customer's browser local storage. The Smart Cart re-applies the cached code on page load, then errors when Shopify rejects it.

Cause: The Smart Cart is evaluating discount eligibility differently than Shopify checkout — usually because the Storefront API is not enabled, so the Smart Cart cannot perform real-time validation against Shopify's live cart.

Fix: enable the Storefront API in the Smart Cart's discount-input configuration.

Cause: The StorefrontDiscount key is missing from the discount payload when the product was added through a Rebuy Smart Cart widget rather than from the PDP. This is a known edge case and may indicate a Rebuy-side bug.

Fix: confirm the Storefront API is enabled in the Smart Cart configuration. If it is enabled and the error persists, reach out to Rebuy Support with your store URL and a reproducible cart link.

Cause: The Shopify Functions discount is hitting Shopify's per-function execution resource limit. This is almost always triggered by unusually large carts (200+ line items), which in practice means bot traffic — legitimate customer carts do not hit this limit.

Fix: safe to ignore for legitimate customers. Rebuy's migration to the new Discount API (built in Rust for higher per-function performance) will resolve this class of error on large carts. If the error is affecting real customers, contact Rebuy Support.

Cause: Your Rebuy session does not have the write_discounts Shopify scope, so Rebuy cannot create the required Automatic Discount. Usually means the email on the Rebuy user does not match the Shopify admin email, or you're logged in as a non-owner staff account.

Fix: clear Shopify and Rebuy session cookies, re-log into Shopify as the store Owner account, and verify the email on the Rebuy user matches the Shopify owner email. Then re-save the Smart Cart.

When the diagnostic checklist does not resolve the issue, work through these debugging steps to isolate the root cause.

Open Shopify Admin → Discounts. Confirm both Rebuy Product Discount and Rebuy Order Discount exist and are in Active status. Expired, Paused, or Scheduled discounts will not apply. This is the single most common root cause and is worth re-checking even if you already have.

The Datasource Previewer is a built-in testing tool that lets you simulate different customer carts and scenarios and see exactly what products the datasource rules would return — before anything goes live. It is the fastest way to confirm whether a rule is actually matching the cart state you expect it to.

Where to find it: Rebuy Admin → Data Sources → select the datasource → Preview Ruleset (inside the datasource settings).

Use it to: verify that the intended products are being returned for a qualifying cart, reproduce the exact cart state you're investigating, and rule out rule misconfiguration before digging into cache, attribution, or Shopify Functions issues.

Open the store in an incognito browser with DevTools → Network tab open. Load the Smart Cart and add a test product. Look for POST requests to Rebuy's discount endpoints. A response body containing "successful": false indicates the discount is failing server-side — check the error payload for the specific reason.

Open the widget in Rebuy Admin and inspect the metafield data for malformed fields, missing widget IDs, or leftover configuration from a previous version. Malformed metafields cause attribution failures that look like "the discount just is not firing."

Then go to https://rebuyengine.com/admin/discounts/ in the browser to see all the live discounts running on the store — not just Rebuy's. Review each discount's metafield data for errors, missing discounts, or malformed data. This view is essential for catching conflicting third-party discounts, duplicate Rebuy discounts, or a missing Rebuy Product Discount / Rebuy Order Discount entry that Step 1 might have passed on a surface check.

In the browser DevTools Console on the storefront, run Rebuy.SmartCart.items() and inspect the properties object of the test line item. Confirm it contains a _rebuy_widget_id (or similar attribution key). Missing attribution means the product was added through a non-Rebuy flow, so the discount will never apply.

You can also check for Rebuy attribution after the order is placed by opening the order in Shopify Admin → Orders and expanding the relevant line item. When an item is purchased through a Rebuy widget, the Shopify order line item carries Rebuy attribution values (for example _rebuy_widget_id and related properties) that identify which specific widget delivered the gift or discount.

If the Shopify order line item does not contain a Rebuy attribution property, the issue is very likely not a Rebuy problem — the product was added through a non-Rebuy flow (PDP direct-add, a third-party app, a Shopify automatic discount, etc.), so Rebuy's discount logic was never in the path. Use this check to quickly rule Rebuy in or out before deeper debugging.

Always re-test in a clean incognito session before escalating.

Note on cancelled orders: If you cancel an order in Shopify and the discount appears to have been stripped from the Admin line-item view, that is a Shopify display behavior — the original charge and discount data are preserved in the order payload and confirmation email. See the FAQ "Why does a Rebuy discount look stripped in Shopify Admin after I cancelled the order?" for the full explanation.

For the full scope matrix with every edge case, see the internal reference "GWP & Discount Promotion Types — Full Reference". The summary below is current as of April 2026.

These are not Rebuy limitations — they are Shopify-platform behaviors that every Rebuy merchant inherits.

Free Rebuy Gift With Purchase items do not count toward Revenue Generated by Rebuy (RGR) calculations or Rebuy billing tiers. Only items with a non-zero post-discount price are counted, and they are counted at their discounted price — not their original price. A $0 gift returns zero billable revenue.

A Rebuy Gift With Purchase discount can still appear in Shopify's order confirmation email or order.json even after the gift was removed at checkout. This is Shopify's behavior — once Shopify writes a discount line into the order payload, the line persists in the stored order object. Rebuy cannot retroactively edit that record. This is cosmetic only and does not charge the customer.

For Gift With Purchase (GWP) Widgets — use the built-in Exclude Items setting. The GWP Widget has a dedicated "Exclude Items" option in its settings that ignores gift cards (and digital items) from cart totals, line counts, and item counts — so they will not count toward the GWP qualifying threshold. Path: GWP Widget's editor → Widget Settings → General → Exclude Items → check Gift Cards (and Digital Items if also needed). This setting is available on GWP Widgets only — it does not appear on other widget types.

For the Tiered Progress Bar (TPB) — use the "Search Products to Exclude" setting (Shopify Functions only). The Tiered Progress Bar has its own exclusion setting that lets you exclude specific products or variants (including gift cards) from counting toward the TPB's unlock subtotal and from receiving the tier's Order Discount. It requires Rebuy's Shopify Functions to be enabled on the TPB.

Path: Smart Cart → Tiered Progress Bar settings → enable Use Shopify Functions (Recommended) → use the Search Products to Exclude input to select the products or variants to exclude → save.

Important TPB-exclusion behavior:

For any other widget type, or for more granular control: add a Cart Does Not Contain rule to the widget's datasource that targets the specific gift card product. This auto-removes the free gift whenever a gift card is in the cart and works across widget types that do not have the built-in Exclude Items or Search Products to Exclude toggle.

Shopify strips the discount from the Admin line-item view when an order is cancelled. This makes it look as though the customer was charged full price. The discount data is preserved in the order confirmation email and the order.json payload — the original charge was correct. This is Shopify behavior, not a Rebuy bug.

If the GWP watcher (GWP validation logic) is auto-removing a gift at Shopify checkout even though the customer's cart still meets the widget's eligibility rules, the root cause is almost always one of the following. The watcher treats each of these as a reason to remove the gift as a safety measure — not because the customer failed to qualify on subtotal or product rules:

Other possibilities to rule out: the cart is being evaluated in a non-default currency on a Shopify Markets store with fixed pricing (see the Shopify Markets edge case in the GWP Validation at Checkout section), or the gift line item lost its Rebuy attribution somewhere in the flow (run Rebuy.SmartCart.items() in the console and confirm the _rebuy_widget_id property is present). See the GWP Validation at Checkout section for the full requirements and decision matrix.

Whether a discount code stacks with a Gift With Purchase depends on Shopify's combinability rules, which Rebuy cannot override. Three scenarios cover the majority of cases:

Additional edge cases to watch for:

A specific discount code can trigger a Gift With Purchase by pairing the GWP widget with the IF Discount Code data source rule. In the GWP widget's data source, set the IF rule to Discount Code, choose Equals or Contains, enter the code, and set the RETURN to a Specific Product (the gift). The Discount Code data source rule reads only codes the shopper enters, so a Shopify discount set to apply automatically with no code is not captured, while the same offer distributed as a code that shoppers type in does fire the rule. The rule is not supported on Post Purchase Offer widgets. For the full rule reference and Buy One Get One setup steps, see Discount Codes as a Condition Input for Data Sources.

The Storefront API is enabled through Smart Cart settings. It turns on automatically the moment a Discount Code Input component is added to the Smart Cart, and the "Use Storefront API" toggle becomes available on that component.

Path: Smart Cart editor → Footer section → Add + → Discount Code Input component → enable Use Storefront API → Save.

Note: The Storefront API is only available on the latest Smart Cart version. Legacy Smart Cart cannot access real-time validation, stacked discount codes, or auto-removal of non-qualifying gifts — so if the Storefront API toggle is not visible, confirm the store is on the latest Smart Cart version first.

Yes. Tiered Progress Bar tiers in Rebuy are triggered exclusively by cart subtotal thresholds, set via the Unlock Price on each tier. There is no built-in setting to change when a tier activates based on other conditions — TPB tiers do not support triggering by specific products in the cart, item count, customer tags, UTM parameters, URLs, or any other rule type.

If you need gift or reward logic that responds to conditions beyond cart subtotal, use a Gift With Purchase Widget (which supports the full Rebuy datasource rule set) or Smart Flows (which supports cart subtotal, item quantity, date ranges, UTM parameters, and more) instead. Both support a much wider range of trigger conditions than the TPB.

Yes — partial discounting is broadly supported across Rebuy widgets. With the single exception of the Tiered Progress Bar's Free Product tier (which is fixed at 100% off), every Rebuy widget that applies a discount to a product can be configured with a specified discount amount — percentage off, fixed amount off, or 100% (free). That includes the GWP Widget, Selectable GWP Widget, Smart Flows BXGY, Post Purchase, Bundle Builder, checkout recommendation widgets, cross-sell and upsell widgets, and the Tiered Progress Bar's Product Discount and Order Discount tier types.

The important nuance: if you need a partial-discount gift product that also auto-adds and auto-removes based on cart conditions (the defining "gift with purchase" behavior — the item appears when the customer qualifies and is removed when they no longer do), that auto-add/auto-remove logic is specifically a feature of the Gift With Purchase Widget, the Selectable Gift With Purchase Widget, and Checkout Extensions recommendation widgets with the Treat as Gift With Purchase setting enabled (Shopify Plus only). Other widgets can apply a partial discount, but they do not include the GWP watcher's rule-based add/remove logic.

So the recommended paths depend on whether the auto-remove behavior is required:

Do not use the Tiered Progress Bar Free Product tier for a partial-discount gift. That tier type is 100% off only — it cannot be configured with any other percentage. Use the Decorative Tier + GWP Widget pairing instead when both a progress-bar visual and a partial discount are required.

Work without the Smart Cart (standalone): Gift With Purchase Widget, Post Purchase Widget, Smart Flows, Bundle Builder's native Gift With Purchase feature, and Checkout Extensions (including the Treat as Gift With Purchase setting on checkout offer widgets).

Require the Smart Cart: All Tiered Progress Bar tier types (Free Product, Product Discount, Order Discount, Free Shipping, Decorative), the Selectable Gift With Purchase Widget (embedded and popup variants), and any pairing that uses a Decorative Tier.

Important — Rebuy no longer supports native Shopify carts as a cart UI. Before the Smart Cart existed, the Rebuy team helped merchants integrate Rebuy widgets into the native Shopify cart (the default cart drawer, flyout, or modal provided by the Shopify theme). That practice has been discontinued. The variation between themes created significant ongoing-support risk and complexity, so Rebuy now prioritizes and supports its own cart product, the Smart Cart. The Smart Cart offers full design customization to match the storefront, plus built-in Rebuy features like automatic discounts, product recommendations, upsells, Tiered Progress Bars, and Selectable GWP — all with full Rebuy support because Rebuy owns the code. Merchants still on a native Shopify cart are recommended to migrate to the Smart Cart. Developers who still need to integrate Rebuy widgets into a native cart flyout, drawer, or modal can follow this guide: How to Add Rebuy to a Native Cart Flyout, Drawer, or Modal. This integration is self-serve and is not supported by the Rebuy team.

Nope! But first, the widget needs to be installed on Shopify. To do that, click the Installation link at the top right of the widget editor and follow the installation instructions. Once installed, you can preview the GWP widget without publishing it live. Just toggle Live Mode OFF in the widget's editor, hit Save, then click the Preview link (also at the top right of the widget editor header). This will take you to Rebuy's Preview Mode on your live storefront, so you can test the widget in action without customers seeing it. See https://help.rebuyengine.com/en/articles/8688905-using-rebuy-preview-mode