Product Warning

What the Product Warning block does

The Product Warning app theme block adds a message area to your product page for QuantityLock. It is designed to support the quantity rules you set in the app, including Minimum Quantities, Maximum Quantities, and your Custom validation messages.

After you add the block to your product template, shoppers can see the warning content in the product page layout instead of only discovering the rule later in the buying process.

The Product Warning block works best when you already have at least one active product quantity limit in QuantityLock.

Before you add the block

  • Make sure QuantityLock is installed and available in Apps in Shopify admin.
  • Create at least one product quantity limit in the app.
  • Add a clear Custom validation message so the warning shown to shoppers is easy to understand.
  • Know which product template you want to update in your Shopify theme.
If this is your first setup, start with one product that already has a simple Minimum Quantities or Maximum Quantities rule so you can test the block quickly.

Add the Product Warning block to a product page

In Shopify admin, go to Online Store and then Themes. On your live theme, click Customize.In the theme editor, use the page selector at the top to switch to a Products template, such as your default product template or the product template you want to update.In the left sidebar, open the main product section that controls your product page layout. This is usually the section that contains the product title, price, quantity selector, and add-to-cart area.Click Add block, open the Apps list, and select Product Warning.Drag the Product Warning block to the place where you want the message to appear. In most stores, the best location is near the quantity selector or the add-to-cart button so shoppers see the rule before adding the item.Click Save in the theme editor to publish the change to that product template.

Where to place the block

The Product Warning block should appear where customers make quantity decisions.

  • Place it near the quantity picker if you want the rule to be visible before shoppers change the quantity.
  • Place it above the add-to-cart button if you want the warning to be part of the purchase area.
  • Avoid placing it too far down the page where shoppers may miss it.
If you add the block to the wrong template, the warning may not appear on the product page you are testing. Always confirm which product template the product is using.

Test the Product Warning block

After saving the block, test the product page on your storefront.

  1. Open a product that has an active product quantity limit.
  2. Check that the Product Warning block appears in the position you chose.
  3. Review the wording shown to shoppers.
  4. Try a quantity below your Minimum Quantities rule or above your Maximum Quantities rule.
  5. Confirm the storefront experience matches the rule and your Custom validation messages.

If the Product Warning block does not appear

First confirm that QuantityLock is installed and opens from Apps in Shopify admin. Then return to Online Store > Themes > Customize, open a product template, and check the Apps block list again.

Make sure the product you are testing has an active product quantity limit in QuantityLock and that your rule includes a clear Custom validation message. Also confirm the block was added to the same template used by that product.

Move the Product Warning block closer to the quantity selector or add-to-cart button in the theme editor, then click Save and test again.

Update your Custom validation messages in QuantityLock so the rule is specific. For example, say the minimum required quantity or the maximum allowed quantity instead of using a generic warning.

Best practices

  • Use the Product Warning block together with active product quantity limits.
  • Keep Custom validation messages short and direct.
  • Place the block close to the quantity and purchase controls.
  • Test one product page before rolling the block out to more templates.

Related pages

Install QuantityLock from the Shopify App Store and access it from Apps in Shopify admin.Create your first product quantity limit and configure Custom validation messages.Learn how QuantityLock blocks invalid quantities and shows shopper-facing validation messages.
Updated May 31 2026
Introduction
Cart Error Handler

Related articles

Cart Error Handler Understand how QuantityLock blocks invalid cart quantities, shows Custom validation messages, and helps shoppers fix minimum or maximum quantity errors. Setup Set up QuantityLock by installing the app, choosing a plan, creating your first product quantity limit, and testing minimum or maximum quantity rules. Installation Learn how to install QuantityLock from the Shopify App Store, approve access, choose a plan, and confirm the app is ready to create quantity limits.

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Introduction

Theme extensions

Product Warning
Cart Error Handler