Because add-in programs aren’t supported in Excel Online, you won’t be able to use the Solver add-in to run what-if analysis on your data to help you find optimal solutions.
If you have the Excel desktop application, you can use the Open in Excel button to open your workbook to use the Solver add-in there. Here’s how:
Click Open in Excel and define and solve a problem by using Solver.
For news about the latest Excel Online updates, visit the Microsoft Excel blog.