Case statement for product template to build accessible breadcrumbs - https://www.shopify.com/partners/blog/breadcrumb-navigation

accessible-breadcrumbs-case-product.liquid

{% when 'product' %}

    {% if collection.url %}
      <li>
        {{ collection.title | link_to: collection.url }}
      </li>
    {% endif %}

    <li>
      <a href="{{ product.url }}" aria-current="page">{{ product.title }}</a>
    </li>