Introduction to Cart Reserve
Cart Reserve is a Shopify app that holds limited inventory as soon as a shopper adds it to cart. It combines a session-based reservation ledger, real Shopify inventory parking, storefront timers, and checkout validation so the same units cannot be promised to multiple shoppers.
It is designed for limited releases, flash sales, product drops, and everyday stores where scarce stock can attract several buyers at once.
The Problem Cart Reserve Solves
Shopify normally resolves competing demand late in the purchase flow. During a traffic spike, several shoppers can believe the same last units are available and only discover the conflict at checkout.
That produces failed checkouts, rushed customers, support tickets, and manual refunds. Cart Reserve moves that decision to the cart interaction and gives an admitted shopper a time-limited claim on the stock.
How a Reservation Works
When a shopper adds an eligible protected variant, Cart Reserve:
- checks stock and the store's concurrent-hold capacity;
- admits the cart or places it in a fair queue during a rush;
- creates a signed, time-limited reservation session;
- moves eligible units from Shopify's available state to its reserved state;
- displays the remaining time on the storefront; and
- validates the reservation and quantity at checkout.
If checkout completes, the reservation is converted. If the shopper removes the item, the hold expires, or the session becomes invalid, Cart Reserve releases the units automatically. Reconciliation workers repair inventory drift if a Shopify request is interrupted.
Inventory Eligibility
Cart Reserve protects Shopify variants according to their inventory settings:
- Tracked, finite inventory — full reservation, real Shopify inventory hold, timer, and checkout enforcement.
- Continue selling when out of stock — a timer and per-cart limits can apply, but checkout is not blocked for stock because Shopify explicitly allows overselling.
- Untracked inventory — no reservation or timer because there is no finite stock to hold.
- Selling-plan lines — subscriptions and prepaid purchase options are not reserved; Cart Reserve protects one-time purchases.
Shopify remains the source of truth for inventory and orders. Cart Reserve temporarily changes the inventory state of eligible units; it never marks a hold as sold.
What Merchants Can Configure
The app includes:
- protected-product selection and per-product quantity limits;
- a fixed or configurable 5–60 minute reservation timer, depending on plan;
- responsive timer presets, translations, and full visual customization on eligible plans;
- a live dashboard, session timeline, conversion metrics, and plan-based history;
- rule-based or AI-powered bot and fraud protection;
- IP and country blocklists plus a global quantity limit on Max.
Plans at a Glance
Reservations are unlimited on every plan. Plans scale by peak concurrent holds, protected products, history, and advanced features.
| Plan | Price | Concurrent holds | Protected products | Highlights |
|---|---|---|---|---|
| Free | $0/month | 25 | 3 | Real inventory holds, fixed 10-minute timer, 1-day analytics |
| Starter | $25/month or $250/year | 100 | 100 | Fair queue, configurable timer, presets, 7-day analytics |
| Pro | $69/month or $690/year | 500 | 500 | AI bot protection, advanced fair queue, full storefront customization, 30-day history |
| Max | $149/month or $1,490/year | 2,500 | Unlimited | ALL-products mode, automatic catalog protection, global inventory limits, blocklists, 90-day history, priority setup support |
Paid plans include a 14-day trial. The Free plan has no trial or time limit. See Subscription & Plans for the complete matrix.
Required Shopify Integration
Full protection requires both Shopify extensions:
- the Cart Reserve app embed detects cart activity and renders the timer; and
- the checkout validation rule rejects protected cart lines without a valid reservation.
Standard themes are detected automatically. Cart Reserve can also analyze custom themes and lets merchants override the selectors used for product forms, cart lines, quantity controls, and timer placement.
Next Steps
Continue to Getting Started for the end-to-end flow, then follow Installation to enable checkout validation, the app embed, product sync, and a protected product.