Shopify: Putting the collection back in breadcrumbs, after fixing the SEO
One of the most common Shopify SEO tips is to remove the | within: collection
filter on the collection template, so that your product links concentrate the link juice to one URL. See the “Duplicate product pages” section of Moz’s guide.
However a side affect of this is that on the product template, the breadcrumbs often rely on using that hint to decide the collection in the breadcrumbs. Leaving you with no breadcrumbs, or a list that just points to your homepage, nowhere else.
This is because the link between a collection and product is a “many to many” connection, meaning a product can exist in many collections and collection can contain many products. So deciding the right collection to link back to from the product page becomes difficult.
The default Shopify method of effectively passing the collection to the products page using the within filter mentioned above, works only from a human perspective, however I would argue that someone is more likely to use the browser back button or gesture, rather than clicking the on page link back to the collection (only my opinion, if you have stats from your store share in the comments).