OOXML (Office Open Extended Markup Language), also called Open XML, is a file format for documents, spreadsheets and presentations that is intended for use with the 2007 and later versions of the Microsoft Office suite. According to Microsoft, OOXML is freely available and can be implemented by anyone using a recent version of Windows. The acronym OOXML is pronounced "oh-oh-XML".
OOXML is the default format for Office 2007 when macros are not enabled. Compatibility packs allow use of OOXML with Office 97, 2000, 2003 and XP. Microsoft has released the beta of a converter intended to facilitate use of OOXML with Macintosh computers. Corel, Novell, Panergy, Datawatch, Gnumeric and several other vendors have announced that new versions of their products, particularly word processors, will support OOXML.
OOXML has been compared with the Open Document Format (ODF) which was developed by a consortium overseen by OASIS (the Organization for the Advancement of Structured Information Standards). There are significant functional and philosophical differences between the two formats. A "standards war" has arisen concerning the relative openness and flexibility of OOXML compared with ODF.
Critics of OOXML contend that it is truly compatible only with Microsoft documents and that its use with products from other vendors appears to have been made difficult by design, while the main goal of ODF has been to ensure interoperability with documents from diverse vendors. Proponents of OOXML counter by pointing out that because it has been developed by Microsoft, OOXML is the format of choice for use with Microsoft documents and offers optimum functionality with those documents, as well as ease of data migration between fixed and mobile computers using Windows. Translators exist that can convert between the two formats.