Inquire

Also known as Spreadsheet Compare, Spreadsheet Inquire or Spreadsheet Management.
This COM add-in allows you to compare versions of a workbook, analyse a workbook for problems or inconsistencies or see links between workbooks or worksheets.
It helps you analyse and review your workbooks to understand their design, function and data dependencies.
This can be used to identify formula errors and broken links.

link - support.office.com/en-gb/article/what-you-can-do-with-spreadsheet-inquire-ebaf3d62-2af5-4cb1-af7d-e958cc5fad42 
link - support.microsoft.com/en-gb/office/turn-on-the-inquire-add-in-6bc668e2-f3c6-4729-8ce1-75ea20aa9d90 
link - youtube.com/watch?v=knIjL0iqh5E (Wyn Hopkins, 5 minute video) 

Dedicated Tab

Workbook Analysis - Produces an interactive report showing structure, formula, cells and warnings. Creates a new workbook.
Workbook Relationship - Displays a graphical map of workbook dependencies to other files.
Worksheet Relationship - Displays a graphical map of worksheet dependencies to other sheets and workbooks.
Cell Relationship - Displays a graphical representation of all the links to (and from) a particular cell.
Compare Files - Lets you compare two workbooks, even VBA code changes.
Clean Excess Cell Formatting - Removes any excess formatting which helps to reduce the file size.
Workbook Passwords - Lets you maintain a list of all passwords.
Help - Provides online help.

Not Available in All Versions of Excel

This is only available in the Professional Plus editions (Office 2013/2016/2019/2021) and Office 365 Enterprise.
This add-in cannot be downloaded from the Microsoft website.

Installing the Add-in

This add-in was the direct consequence of Microsoft's purchase of Prodiance in 2011.
Prodiance developed risk management tools to help audit and assess risk in spreadsheets.