http://api.shopify.com/metafield.html http://wiki.shopify.com/Metafield_%28API%29 Many Shopify resources permit decoration with metafields, which are simple typed, name/value pairs. If you want your app to store some data against specific resources inside Shopify itself, Metafields appear to be the way to do it. They have the benefit of being accessible through Liquid templates on Shopify itself, too.