Office Open XML (also informally known as OOXML or OpenXML) is a zipped, XML-based file format developed by Microsoft for representing spreadsheets, charts, presentations and word processing documents. The format was initially standardised by Ecma (as ECMA-376), and by the ISO and IEC (as ISO/IEC 29500) in later versions.Starting with Microsoft Office 2007, the Office Open XML file formats have become the default target file format of Microsoft Office.