Default file format: registry value defaultformat (excel\options)UserHKCU\software\policies\microsoft\office\16.0\excel\options

Policy ID: L_SaveExcelfilesas
Scope: User Configuration
Supported on: At least Windows Server 2008 R2 or Windows 7
Source: Microsoft 365 Apps / Office Administrative Templates (version 5568.1000)
Category: Microsoft Excel 2016 › Excel Options › Save

Registry

defaultformat

REG_DWORDUser

HKCU\software\policies\microsoft\office\16.0\excel\options Current key

Enabled value: Depends on the option value
Element: Save Excel files as

Options
Item	Stored value
Excel Workbook (*.xlsx)	51
Excel Macro-Enabled Workbook (*.xlsm)	52
Excel Binary Workbook (*.xlsb)	50
Web Page (.htm; .html)	44
Excel 97-2003 Workbook (*.xls)	56
Excel 5.0/95 Workbook (*.xls)	39
OpenDocument Spreadsheet (*.ods)	60

Apply with .reg · CMD · PowerShell

.reg

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\software\policies\microsoft\office\16.0\excel\options]

; Options (use only one)
; Excel Workbook (*.xlsx)
"defaultformat"=dword:00000033
; Excel Macro-Enabled Workbook (*.xlsm)
"defaultformat"=dword:00000034
; Excel Binary Workbook (*.xlsb)
"defaultformat"=dword:00000032
; Web Page (*.htm; *.html)
"defaultformat"=dword:0000002c
; Excel 97-2003 Workbook (*.xls)
"defaultformat"=dword:00000038
; Excel 5.0/95 Workbook (*.xls)
"defaultformat"=dword:00000027
; OpenDocument Spreadsheet (*.ods)
"defaultformat"=dword:0000003c

CMD

:: Options (use only one)

:: Excel Workbook (*.xlsx)
reg add "HKCU\software\policies\microsoft\office\16.0\excel\options" /v "defaultformat" /t REG_DWORD /d 51 /f
:: Excel Macro-Enabled Workbook (*.xlsm)
reg add "HKCU\software\policies\microsoft\office\16.0\excel\options" /v "defaultformat" /t REG_DWORD /d 52 /f
:: Excel Binary Workbook (*.xlsb)
reg add "HKCU\software\policies\microsoft\office\16.0\excel\options" /v "defaultformat" /t REG_DWORD /d 50 /f
:: Web Page (*.htm; *.html)
reg add "HKCU\software\policies\microsoft\office\16.0\excel\options" /v "defaultformat" /t REG_DWORD /d 44 /f
:: Excel 97-2003 Workbook (*.xls)
reg add "HKCU\software\policies\microsoft\office\16.0\excel\options" /v "defaultformat" /t REG_DWORD /d 56 /f
:: Excel 5.0/95 Workbook (*.xls)
reg add "HKCU\software\policies\microsoft\office\16.0\excel\options" /v "defaultformat" /t REG_DWORD /d 39 /f
:: OpenDocument Spreadsheet (*.ods)
reg add "HKCU\software\policies\microsoft\office\16.0\excel\options" /v "defaultformat" /t REG_DWORD /d 60 /f

PowerShell

# Common: create the key
New-Item -Path 'HKCU:\software\policies\microsoft\office\16.0\excel\options' -Force | Out-Null

# Options (use only one)
# Excel Workbook (*.xlsx)
New-ItemProperty -Path 'HKCU:\software\policies\microsoft\office\16.0\excel\options' -Name 'defaultformat' -PropertyType DWord -Value 51 -Force | Out-Null
# Excel Macro-Enabled Workbook (*.xlsm)
New-ItemProperty -Path 'HKCU:\software\policies\microsoft\office\16.0\excel\options' -Name 'defaultformat' -PropertyType DWord -Value 52 -Force | Out-Null
# Excel Binary Workbook (*.xlsb)
New-ItemProperty -Path 'HKCU:\software\policies\microsoft\office\16.0\excel\options' -Name 'defaultformat' -PropertyType DWord -Value 50 -Force | Out-Null
# Web Page (*.htm; *.html)
New-ItemProperty -Path 'HKCU:\software\policies\microsoft\office\16.0\excel\options' -Name 'defaultformat' -PropertyType DWord -Value 44 -Force | Out-Null
# Excel 97-2003 Workbook (*.xls)
New-ItemProperty -Path 'HKCU:\software\policies\microsoft\office\16.0\excel\options' -Name 'defaultformat' -PropertyType DWord -Value 56 -Force | Out-Null
# Excel 5.0/95 Workbook (*.xls)
New-ItemProperty -Path 'HKCU:\software\policies\microsoft\office\16.0\excel\options' -Name 'defaultformat' -PropertyType DWord -Value 39 -Force | Out-Null
# OpenDocument Spreadsheet (*.ods)
New-ItemProperty -Path 'HKCU:\software\policies\microsoft\office\16.0\excel\options' -Name 'defaultformat' -PropertyType DWord -Value 60 -Force | Out-Null