Crabapples are edible, notes Clemson Cooperative Extension, but eating them can be unpleasant. If the crab apples measure 2 inches in diameter or larger, they are considered more pleasant for human consumption than smaller crabapples.
Crabapples, especially larger ones, are used to make condiments, such as tart jelly, jam and fruit sauces. No extra thickener is required for this type of jelly because the fruit naturally contains pectin, which makes the crabapple juice and sugar turn into a gel when boiled. While not typically enjoyable for humans to eat, small, ornamental crabapples have a bitter and sour flavor that is suitable for some animals and for bird consumption. These provide wildlife with a winter food source.