User Configuration > Administrative Templates > Microsoft Office 2016 > Services
User
HKCU\software\policies\microsoft\office\16.0\common\options
This policy setting controls whether alternative text (alt text) is generated automatically for pictures in Word, PowerPoint, and Outlook. This policy setting is related to the "Automatically generate alt text for me" check box under File > Options > Ease of Access > Automatic Alt Text. If you enable this policy setting, alt text will be generated automatically for pictures. The "Automatically generate alt text for me" check box will be selected and users won't be able to clear the check box. If you disable this policy setting, alt text won't be generated automatically for pictures. The "Automatically generate alt text for me" check box won't be selected and users won't be able to select the check box. If you don't configure this policy setting, alt text will be generated automatically for pictures. But, users will be able to clear the "Automatically generate alt text for me" check box.