Even if you’ve been coasting through Excel without fully understanding what’s happening on every sheet you open, you’ve probably noticed curly brackets appearing in some formulas — even though you never typed them yourself. If you don’t feel like a spreadsheet wizard, it’s easy to ignore them, especially when all your formulas are working as expected. However, if you’re anything like me and tend to question things that show up without a clear explanation, those brackets are hard to overlook. You’ll be wondering why they’re in your formulas and whether they signal something important. Do they point to a useful feature working behind the scenes, or are they a warning that something unusual is going on? Legacy array formulas The curly brackets you can’t type yourself Screenshot by Ada The most common type of curly brackets you’ll find in Excel formulas is the one wrapped around a formula expression, like this: {=SUM(I2:I100*J2:J100)} This kind of formula is known as a legacy array formula, sometimes referred to as a CSE formula. The name comes from the …