While both active dry yeast and instant yeast are used for baking, they differ in many ways. Active dry yeast requires to be rehydrated before use, while instant yeast does not need to be rehydrated and is typically added directly to the dough. Active dry yeast generally requires a longer fermentation period as compared to instant yeast, as its cells take longer to become fully activated. This means that recipes calling for active dry yeast may require more rising time than those utilizing instant yeast. Additionally, active dry yeast is not as finely milled as instant yeast, which can also affect how quickly the dough ferments. When substituting one type of yeast for another, it is essential to note that active dry yeast will result in a slightly slower rise than what would occur with the same amount of instant or rapid-rise yeast.  To achieve optimal results when replacing active dry with instant or rapid-rise, reduce the amount of the latter by 25% because it is much more potent than the former. For example, if a recipe needs 1 teaspoon of active dry yeast, replace it with ¾ teaspoon of either instant or rapid-rise. Finally, it's best to proof any kind of baking yeasts before using; however, this step is especially important when using active dry yeasts since they can go stale or have been stored incorrectly due to their low moisture content.