Supercook.com and AllRecipes.com provide recipe searches by ingredients. Supercook.com also allows the user to refine the search by food restrictions, cuisine type and specific meals.
Supercook.com automatically narrows down recipes as the user clicks on ingredients from the left side of the page. For example, as of 2015, clicking on cheddar, eggs, flour and onion results in more than 100 recipes the user can prepare from tempura batter to egg noodles. The website notifies the user if more ingredients are required to complete each recipe.
AllRecipes.com’s ingredient search only allows four entries and does not allow search refinement. The above ingredient search yields more than 200 recipes.