Data validation is a feature in MS Excel used to control what a user can enter in a cell of an excel sheet. Like, restrict entries in a sheet, such as a date range or whole numbers only. We can even create dropdowns as well, which saves un-necessary space and shows the values in a single cell. Also, we can create a customized message which will appear user insert any incorrect value or an incorrect format.

As an example, A user can specify a meeting scheduled between 9:00 AM and 6:00 PM.

As we can use data validation in excel to make sure a value is a positive number, a date between 15 and 30, make sure a date occurs in the next 30 days, or make sure a text entry is less than 25 characters etc.

Working with validations on an Excel file.