Startup Switches

When you open Excel a lot of the settings are read from the Windows Registry, including details of any built-in add-ins that are currently installed.
There are a number of command line switches that can also be used to affect the way that Excel starts.
These switches can be added to the Properties of a shortcut that starts Excel.

/safemode	Opens Excel ignoring all the Startup Folders and All Add-ins, including VBA Add-ins, Automation Add-ins and COM Add-ins. This is the same as holding down the Ctrl key when you start Excel.
/safe	Same as above
/s	Same as above
/a progid	Opens Excel and loads the Automation Add-in with the corresponding ProgID. excel.exe /a MyProgID.Name
/automation	Opens Excel ignoring all the Startup Folders and any VBA Add-ins.
/embedded	Opens Excel in Embedded mode which prevents the default workbook Book.xltx from being created.
/embed	Same as above
/e	Same as above
/m	(Redundant) Opens Excel with a new workbook containing a single Excel 4.0 macro sheet.
/n filepath	Opens Excel using a specified file as a template for the default workbook. excel.exe /n "c:\temp\MyBook.xlsx"
/o	Opens Excel forcing it to re-register itself in the Window Registry.
/p folderpath	Opens Excel overriding the default local file location user option with a new folder path.
/r filepath	Opens Excel with a specific file in read-only mode. You must include the path and filename afterwards.
/t filepath	Opens Excel using a specified file as a template for the default workbook. excel.exe /t "c:\temp\MyBook.xlsx" excel.exe /t http://mysite.com/MyBook.xlsx
/x	Starts a new instance of Excel as a separate process.
/regserver	Forces Excel to re-register itself in the Windows Registry and then quit.
/unregserver	Forces Excel to unregister itself in the Windows Registry and then quit.
filepath (no switch)	Starts Excel and opens a specific file. This parameter does not require a switch excel.exe "c:\temp\MyBook.xlsx" excel.exe https://MySite/Book1.xlsx

Using (Start > Run)

The easiest way to run Excel with additional switches is to use the Command Line.
All you need to do is select (Start > Run) and type the full folder path of the Excel.exe file.
This folder path needs to be enclosed in parentheses with the corresponding startup switch added afterwards.
You will probably need to change the folder path, the one shown here corresponds to a Microsoft 365 installation.
"C:\Program Files\Microsoft Office\root\Office16\EXCEL.EXE" /s

Safe Mode

When you open Excel in Safe mode this will be displayed in the Title bar.