Can I Swap Light Brown Sugar For Dark And Vice Versa?

Can I swap light brown sugar for dark and vice versa?

Even though light and dark brown sugar are often used interchangeably (and some recipes do work with both), they differ in their molasses content, which in turn affects their moisture level and pH. Chris Morocco’s recipe for BA’s Best Chocolate Chip Cookies, for example, calls for dark brown sugar. When Sohla made them with light brown they spread pancake-thin on the baking sheet. The more acidic dark brown sugar was meant to help activate the baking soda and cause the cookies to puff in the oven. Light brown sugar just didn’t have the same oomph and, thus, skinny cookies.