Microsoft Add-Ins do not use the default browser you have chosen for your OS when running on Microsoft Windows. Learn how to tell which browser is used for your add-in below.
The version used is dependent on the combination of your Operating System and Office Version.
Beginning with Office 365 version 16.0.11629 and Windows 10 version 1903, Office Add-ins running on Office 365 for Windows will use Microsoft Edge.
To clear Edge cache follow the instructions here.
All lower versions of Windows and Office will use Internet Explorer (IE). To clear IE cache follow the instructions here.
Add-Ins on a Mac will always use the default browser you have selected for your OS (ie Chrome, Safari, etc.)