Sometimes when you open a document in Microsoft Word 2016, you will see the text [Compatibility Mode] in the title. As you may be aware each new version of Word introduces new features that were not supported by previous versions. This means that a document that was created by Word 2003, for example, will not have been created using the new features specific to Word 2016. When you open this document in Word 2016, [Compatibility Mode] is displayed in the title to let you know this.
You can easily convert the document to the Word 2016 and enable all Word 2016 features by clicking File > Info > Convert. When you do so, you will see the following informational message:
This is nothing to worry about, and you can click OK to continue with the conversion. In essence, the act of conversion will make the new Word features available, but may also cause some minor layout changes in the document. Converting the document also reduces its size.
Note that converting the document may change its file extension. If you convert a .doc document, it will become a .docx document. While you remain in the document, though, its title will still display the .doc extension – until you save the document.