Catsup.io is a niche editorial site billed as the internet's most comprehensive resource dedicated to the history, science, culture, and future of catsup — the older American spelling of ketchup. It traces the condiment's journey from fermented fish pastes in 17th-century Southeast Asia to the tomato-based staple now found on an estimated 97% of American tables, while diving into the catsup-versus-ketchup spelling debate, regional taste differences, and the question of who actually invented it. The site is structured around five main sections — Learn (ingredients, nutrition, gluten-free and FODMAP info), Recipes (homemade versions including Heinz copycat, sugar-free, fermented, banana, mushroom, blueberry, mango, and walnut catsup), Brands (Heinz, Hunt's, Brooks, Del Monte, French's, Red Gold), Storage (shelf life, freezing), and Types (fancy, Mexican, Chinese, colored) — plus quirky curiosities like the world's largest catsup bottle, pop culture appearances, and stain removal tips.