Crabapples are safe to consume as long as you don’t eat too many of them. Actually, the only difference between crabapples and apples is the size of the fruit. By definition, crabapples have fruit that are 2 inches or less in diameter, and apples are more than 2 inches in diameter. By this definition, most of the apples grown from seed will be crabapples. The fruiting apples are grafted.
So, did people ever plant crabapples from seed? Of course they did. Just think of Johnny Appleseed. But those apples were normally used for jelly, applesauce, and cider and not for fresh eating.
There is one other caveat with using crabapples from a tree in the landscape. Make sure the tree hasn’t been sprayed as an ornamental with a pesticide that isn’t labeled for fruit tree apples. If it has, then the fruit should not be used. (Ward Upham)