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Overview

This setting does two things:
  1. Queues Shopify Ajax cart calls. When several scripts hit Shopify’s Ajax cart API (/cart/add, /cart/add.js, /cart/update.js, /cart/change.js) at the same time, Shopify sometimes drops one of the changes. Upcart forces those calls to run one at a time so every update registers. This is the setting’s main purpose.
  2. Steps back from Add to Cart. It also disables Upcart’s built-in Add to Cart handling, so an app or theme that needs full control of that flow doesn’t conflict with it.
Both behaviours are tied to the one checkbox — you can’t enable the request queueing without also giving up Upcart’s Add to Cart handling.

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Where to Find It

Open the cart editor, go to Settings > Cart settings, and expand Advanced Settings.
Look for “Enhanced Ajax API compatibility.”

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How It Works

Upcart maintains full control over the Add to Cart process. This ensures consistent behavior and allows Upcart to prevent other apps or scripts from overriding the cart flow. This is the recommended setting for most stores. Keep this disabled unless you are experiencing specific issues where Upcart is not intercepting add-to-cart events from your theme or other apps.

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Enabled

Upcart will no longer manage the Add to Cart process. This allows other apps, custom JavaScript, or your theme to modify the cart without interference. Enable this setting ONLY when:
  • Your store uses a non-standard AJAX cart API
  • Upcart is not intercepting add-to-cart events from your theme or other apps
  • You need third-party apps to have direct control over cart behavior
Important trade-offs when enabled:
  • Other apps can redirect customers to the Shopify cart page instead of opening the Upcart drawer
  • You may experience redirect loops or unexpected cart behavior
  • Upcart cannot prevent external apps from altering cart behavior
If enabling causes redirect loops:
  1. Disable this setting
  2. Use the manual Upcart API (upcartRegisterAddToCart) instead
  3. See integration guides for specific apps (e.g., Replo)

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Testing

After changing this setting:
  1. Click Save
  2. Test adding products to your cart
  3. Verify the Upcart drawer opens correctly
  4. Check that you’re not redirected to the Shopify cart page
If you experience issues after enabling, disable the setting and contact support for alternative solutions.