Sweet, tangy tomato-based condiment. Used as a dip, glaze ingredient, and base for barbecue sauces.
Substitutes
Tomato Paste — 1 tbsp tomato paste + 1 tbsp vinegar + 1 tbsp sugar per 3 tbsp ketchup. Mix tomato paste with vinegar and sugar to recreate ketchup's sweet-tangy balance.
Tomato Sauce — 1/4 cup tomato sauce + 1 tbsp vinegar + 1 tbsp sugar per 1/4 cup ketchup. Tomato sauce with vinegar and sugar approximates ketchup. Cook down slightly to thicken.
Mustard — 1:1 (as condiment substitute). Very different flavor but fills the same condiment role. Sharp and tangy instead of sweet.
Hot Sauce — 1-2 tsp hot sauce per 1 tbsp ketchup. Hot sauce adds heat and tang. Use much less. Mix with a little sugar for closer approximation.