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Office Open XML I: Exploring the Office Open XML Formats

Compressed folder containing various document components

The Office Open XML Formats use ZIP technology to automatically compress and compartmentalize the content in your 2007 Office system documents.

The Office Open XML Formats reduce file size, simplify document troubleshooting, and make it easier to protect sensitive information in your documents. How do they do it?

  • The new file formats use ZIP technology to compress files automatically. Without the need for any other software, your files are compressed each time you save them, keeping file sizes much smaller than with the previous Microsoft Office document formats.
  • Office Open XML Format files are modular — different types of information are stored independently. Each document is actually a ZIP package containing several files, such as one for the document body, one for headers, and one for comments. So if an error occurs in one document component, other components remain unaffected, greatly simplifying content recovery.
  • XML is a markup language, similar to the concept of marking up a document to make changes. That is, the document content as well as the data saved by Word, Excel, or PowerPoint to format and manage that content is equally accessible. So you can easily access the information contained in your documents and help avoid sharing sensitive information.


  • Although an Office Open XML Format document contains several files, you never have to see those separate files unless you do so intentionally. Using the new formats does not require you to do anything differently when you create documents.
  • The file types you know from previous versions of Microsoft Office (such as .doc for Word, .xls for Excel, and .ppt for PowerPoint — often referred to as the "legacy" file formats) are still available.
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