MaxQty Guard — Per‑Product Limits & Alerts
The Opportunity
No‑code app to set max (and min) purchase quantities per product or variant with real‑time cart alerts. Enforces limits across cart, dynamic checkout, and draft orders to prevent bypasses and reduce support tickets.
"Merchants need to cap how many units of a single product a customer can purchase in one order and show a clear alert when the cap is reached, but existing code snippets are outdated and many apps don’t work reliably with modern themes or accelerated checkouts."
Market Validation
Detailed Analysis
Proposed Solution
Provide a rules UI to set per‑product/variant max quantities (e.g., max 3) and a theme app extension that blocks additions beyond the limit with user‑friendly messages. Use server‑side validation (Shopify Functions) to enforce limits even if the cart UI is bypassed (e.g., Buy Now, Shop Pay).
Target Audience
Shopify merchants (SMB to mid‑market) needing scarcity controls or fair‑purchase policies for limited items.
Competitive Landscape
Order Limits (MinMaxify), OrderLogic — Min & Max Rules (Oiizes), Min&Max Limits by Easify, KOR Order Limit & Min‑Max, MinCart — Min/Max Order Limits, BSS Commerce Min/Max Quantity
Implementation Notes
Build a Shopify app with: (1) Shopify Functions for Cart and Checkout Validation to enforce per‑line item caps server‑side; rules stored in app DB and synced to product metafields for speed. (2) Theme App Extension injecting a lightweight script to intercept cart/add and cart/update events and show localized alerts when max is reached, and to disable increment controls in cart drawers/pages. (3) Support dynamic checkout (Shop Pay/Buy Now) by relying on the validation function to fail the add/checkout with a friendly error. (4) Admin UI for global defaults, product/variant overrides, and exceptions; bulk editor and CSV import. (5) Multi‑language copy via Translations API; compatibility with selling plans/subscriptions and bundles using the new cart transform APIs. (6) QA across Online Store 2.0 themes, cart drawers, and headless storefronts using Storefront API/cart endpoints.
Evidence from Merchants
Real quotes from Shopify community forums
"we can´t sell more than 5 pices of the same product per client and we try to ajust that quantity but we try whit 4 apps and none work."
"I can’t find out how to limit the quantity of one product that a customer can add to cart per transaction, without buying another app."
"I want to restrict customers from adding more than 3 quantities of a single item to their cart."
Key Pain Points
Inability to limit product quantities leading to potential revenue loss and customer dissatisfaction.
criticalMentioned by 3 merchants
Impact: Potential loss of sales due to customers being able to purchase excessive quantities.
Market Metrics
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