I can't remember whether to use parchment paper or wax paper when baking cookies in the oven.
Does anyone know which one?
I always use parchment paper.
Absolutely Parchment paper. Wax paper will melt (don't ask how I know this....).
People have been baking with waxed paper for eons. Parchment paper is the newcomer. HTH
For cookies you need parchment, the waxed paper can burn. For lining a pan that will be covered with batter, for instance brownies or cake you can use either.
I switched over to ONLY parchment paper some years ago. The difference is that parchment paper can be used to roll out cookie or pastry dough, frozen, and then baked straight from the freezer. Wax paper gets soggy and disgusting when you freeze it in contact with dough.