Set up your rule
Open Discount Guard
In Shopify Admin, go to Apps and open Discount Guard. No theme changes are needed.
Choose your promotion group
Select discount codes from your Shopify discount list, then choose Apply selection. For example, put PROMO-A and PROMO-B in this group. Select 1–100 codes; the other entered codes belong to the additional group.
Write your checkout message
Enter a message of 1–120 characters for customers whose extra code is rejected. Changing the console language does not translate this customer-facing message.
Enable and save
Turn on Enable checkout protection, then choose Save rules. Confirm that the status is Enabled. Applying a picker selection alone does not save your rule.
Test a real checkout
Use eligible, combinable test codes. Check one promotion plus one additional code, two promotion codes, and two additional codes. Also enter codes directly at checkout.
How codes combine
Each order has a limit of one code from your promotion group and one code outside that group. Automatic discounts do not use either slot. Shipping discount codes do count; gift cards are a payment method and do not count.
Among codes Shopify allows the app to reject, the last code supplied to the Function in each group is kept. A protected code takes priority in its group. Shopify still decides which codes are eligible and which discounts can combine.
Example: PROMO-A and PROMO-B are in the promotion group. BONUS-A and BONUS-B are additional codes.
Percentage and fixed amount codes use the same count rules. The app does not recalculate discounts or merge codes. Amounts, minimum spend, customer eligibility, usage limits and combination settings stay in Shopify Discounts. An allowed count does not make an otherwise invalid combination work.
Pause or uninstall
Choose Pause protection in the app to stop the count rule. Your saved promotion group and checkout message are preserved. To resume, enable checkout protection and save the rules again.
To remove the app, go to Shopify Settings → Apps and sales channels, find Discount Guard and uninstall it. After Shopify's uninstall notification is processed, the app deletes that store's active database records. Your original merchant-created coupons remain in Shopify. Retention and backups are explained in the privacy policy.
Common questions
Does it work when a customer skips the cart?
Yes, when protection is enabled. The rule runs inside Shopify's discount calculation through a Shopify Function. It does not rely on cart page JavaScript. Shopify determines which entered codes are available to the Function.
Do automatic discounts, shipping codes or gift cards count?
Automatic discounts do not count. Entered shipping discount codes count toward their assigned group, just like other codes. Gift cards are a payment method, so they do not count.
Can I use percentage and fixed amount coupons?
Yes. Discount Guard counts codes rather than calculating discount amounts. Shopify applies the original values and its own calculation and combination rules.
What does a Shopify protected code mean?
Shopify supplies a rejectable flag for each entered code. If rejectable is false, this app must leave the code alone. Such a code takes priority over rejectable codes in its group. Multiple protected codes in one group can exceed the limit because the app cannot reject them.
Why is a code still not working, or why are too many codes allowed?
Check that protection is Enabled and your group was saved. Check each original discount's dates, eligibility and combination settings. Confirm which group each code belongs to, then check whether Shopify protected any codes from rejection. A missing or invalid rule configuration does not reject codes.
Does this stop someone from using a coupon that is not theirs?
Discount Guard limits the number of entered codes. Restrict a coupon to its intended customers using the eligibility settings on the original Shopify discount. This app does not verify customer ownership.
Does the app create replacement coupons or change my theme?
No replacement coupon codes or theme changes are required. Saving the rule creates or updates the app's own automatic discount rule in Shopify. That rule provides the rejection behavior and adds no discount amount. Usage statistics remain attached to the original coupons.
What should I do if saving reports a conflict?
Refresh the app before trying again. Another tab may have changed the settings. If the app reports duplicate Discount Guard rules or cannot locate a rule safely, contact support with the exact message instead of creating more rules.
What data does the app store?
It stores the shop identity, an encrypted Shopify authorization session and a reference to the app's rule in Cloudflare D1. Rule settings live in Shopify. Read the privacy policy for permissions, providers, retention and deletion.