With Macie, you can add custom-defined data types using regular expressions to help Macie discover proprietary or unique sensitive data for your business. For example, you might have a specific format for your employee IDs; a possible format is to have a capital letter, which defines if someone is a full-time or part-time employee, followed by a dash, and then eight numbers (such as F-12345678 for a full-time employee). These custom sensitive data types defined are unique to each customer and are not shared with other customers.