Microsoft Office add-ins are tools that can be installed within the Office applications to enhance their functionality, providing new features and capabilities without requiring a switch between programs. These add-ins can be used with both free Office Online apps and newer versions of Office for Mac and Windows. The selection process involved over 100 highly-rated apps across four main products (Outlook, Word, Excel, and PowerPoint), narrowing down to the top 22 add-ins that meet specific criteria such as being free, having broad audience appeal, and offering useful use cases. Some popular add-ins include Boomerang for Outlook, Woodpecker for Word, XLTools.net Data Cleaning for Excel, Pickit for PowerPoint, and Zapier for automating Office apps with other tools. These add-ins can greatly enhance productivity and efficiency in various tasks such as email management, document creation, data analysis, presentation design, and more.