One question I get asked all the time is whether it is acceptable to use salted butter in baking, since most recipes either don’t specify salted or unsalted, or explicitly recommended unsalted butter.
The simple answer is that yes, it is fine to use salted butter in baking. That being said, there is a reason that bakers – myself included – and just about all other cooks use unsalted butter as their kitchen staple instead of salted.
Salt serves two roles in butter, acting as a preservative and as a flavoring agent. Since refrigeration is so reliable these days, the vast majority of us don’t need to give butter spoilage a second thought (especially if you go through it quickly in baking!), so flavor is paramount. Salted butter tastes great on toast and in other foods because the salt will bring out not only the butter flavor, but the other flavors of whatever you’re eating. In fact, you probably won’t need to add salt at all, if you’re using salted butter in your cooking, and this is exactly why salted butter is not idea for baking.
Baked goods, especially that require some leavening, often count on the inclusion of salt to enhance flavor and to ensure the best rise (from cookies, muffins, breads, etc) possible. But recipes tend to specify a small amount of salt in their ingredients and this is where salted butter falls short: you can’t control the amount of salt that is in the butter. Omitting the salt called for and using salted butter might turn out a result that is just right, but your dish might not have enough salt in that case. The opposite extreme is that your dish might have way too much salt in it, since salted butters can contain anywhere from 1/4-3/4 tsp of salt per half cup.
Odds are, whatever you’re making will probably turn out just fine if you use salted butter, but the risk of getting something a little funky is there – and it isn’t when you stick with unsalted and have absolute control over the amount of salt you use. I’d recommend sticking with unsalted for baking and saving salted for cooking (where flavors are easily forgiven/altered with other spices) or spreading on really good bread.