The EU executive will investigate if steps announced by Microsoft to make it easier for users of an open-source rival to work with Microsoft Office would give consumers greater choice.
"The Commission will investigate whether the announced support of ODF (Open Document Format) in Office leads to better interoperability and allows consumers to process and exchange their documents with the software product of their choice," it said in a statement on Thursday.
Microsoft said on Wednesday that starting some time next year it will make it easier for users of an open-source rival to work with Microsoft Office.
Without adding any special software to Office, users will be able to open documents sent to them in the open source Open Document Format (ODF), the company said. Users will also be able to edit and save documents in that format.
The Commission has fined Microsoft 1.68 billion euros ($2.7 billion) since 2004, in large part for the company's failure to provide proper interoperability between its dominant Windows operating system and other software.