.OPAL File Extension
File TypeMicrosoft Office User Settings File
What is an OPAL file?
Contains language specific resources used by the Office Customization Tool (OCT) to customize how Microsoft Office is installed; includes resources specific to a particular language like US English, German, Spanish, etc...
OCT allows users to customize the default settings that will be in Microsoft Office when it is installed. Examples of default settings would be default font size, autocorrect options, or file validation options.