Shopify Cart Missing Personalization Option

1. Line-item key prefixed with underscore (28%)

Shopify convention: property keys starting with _ are hidden from the cart display. Used intentionally for fulfillment metadata (_photo_url, _dpi) that customers shouldn't see. If your customer-facing property is named _custom_text, rename to Custom text. Underscore-prefixed properties still persist on the order — they just don't show at cart.

2. Cart template missing the properties loop (19%)

Many themes' cart template renders just the product title + quantity + price, no property loop. Add to sections/main-cart-items.liquid (or your theme's equivalent):

{% for property in item.properties %}
  {% assign key = property.first %}
  {% assign value = property.last %}
  {% unless key contains '_' %}  {# skip underscore-prefixed #}
    <div class="cart-item__property">
      <strong>{{ key }}:</strong> {{ value }}
    </div>
  {% endunless %}
{% endfor %}

3. Cart drawer + cart page templates diverged (14%)

Your cart page shows properties but the cart drawer doesn't (or vice versa). The drawer lives in snippets/cart-drawer.liquid or sections/cart-drawer.liquid — a separate template. Duplicate the properties loop into both templates.

4. App's "show in cart" toggle off (12%)

Personalization app admin → Options → each option → "Show in cart" toggle. Merchants sometimes turn this off during setup and forget. Turn it back on.

5. Add-to-cart AJAX loses properties (10%)

A theme's custom JS makes an AJAX add-to-cart call but doesn't pass the personalization properties. Check the network tab in DevTools when adding to cart — the request body should include a properties object. If missing, the theme's JS needs to serialize properties from the personalization form:

const formData = new FormData(form);
const properties = {};
formData.forEach((value, key) => {
  if (key.startsWith('properties[')) {
    const propName = key.match(/properties\[(.+)\]/)[1];
    properties[propName] = value;
  }
});
await fetch('/cart/add.js', {
  method: 'POST',
  body: JSON.stringify({ id: variantId, quantity: 1, properties }),
  headers: {'Content-Type': 'application/json'}
});

6. Cart drawer cached with stale HTML (7%)

The theme's drawer renders once on page load, and the cached HTML doesn't reflect new properties. Fix: after add-to-cart, refetch cart HTML with fetch('/?section_id=cart-drawer').then(r => r.text()).then(html => updateDrawer(html)).

7. Property value contains HTML or JS (5%)

Customer typed <script> or <div> in the personalization field. Some themes strip these values entirely as XSS protection. Fix: escape but don't strip — use {{ value | escape }} in the theme template.

8. Empty-value properties sanitized (5%)

Customer left an optional field blank. Some themes' add-to-cart JS filters out empty-value properties before submitting. Result: "Gift message" property is absent when the customer skipped it. Usually benign — but if you rely on the property being present, add default values in your form.