What is the difference between All Purpose Flour and Cake Flour?

The significant difference between all-purpose flour and cake flour is the amount of protein that each flour has.

The protein contains in the flour determines how much gluten the flour has. This, in turn, has an effect on the texture of what you baked. The more the protein, the denser, and stronger the texture. The lesser the protein, the lighter the texture.

All-purpose flour has about 10 to 12% protein. The higher protein content will allow the flour to absorb more water, producing stiffer dough.

All-purpose flour is best for pastries such as cookies
On the other hand, cake flour contains only 6 to 8% protein. This absorbs less water producing soft, moist, and pliable dough.

Cake dough is the preferred option for cake baking.

The most significant difference between cake and all-purpose flour is the amount of protein contained in it. The protein in the flour influences the amount of gluten created while kneading the flour. Gluten is the ingredient that makes the end product either tough as in bread or airy and flaky as in cakes or pastries.

Cake flour is called "weak" flour as it’s key ingredient is soft wheat. All-purpose flour lands somewhere in between weak and strong as it requires something like bread flour, which includes more hard wheat to be called strong flour.

All-purpose flour is not as intricately ground as cake flour due to which there is a difference in texture. Cake flour is composed of soft wheat, while all-purpose flour is a combination of both.