Word document (docx) -
DOCX is the file format for Microsoft Office 2007 and later.
DOCX should not be confused with DOC, the format used by earlier versions of Microsoft Office.
Container Format
DOCX is written in an XML format, which consists of a ZIP archive file containing XML and binaries. Content can be analysed without modification by unzipping the file (e.g. in WinZIP) and analysing the contents of the archive.
The file _rels/.rels contains information about the structure of the document. It contains paths to the metadata information as well as the main XML document that contains the content of the document itself.
Metadata information are usually stored in the folder docProps. Two or more XML files are stored inside that folder, app.xml that stores metadata information extracted from the Word application itself and core.xml that stores metadata from the document itself, such as the author name, last time it was printed, etc.
Another folder contains the actual content of the document, in a Word document, or an .docx document the folder's name is word. A XML file called document.xml is the main document, containing most of the content of the document itself.
Relationship to OOXML
Office Open XML is an open XML standard developed by Microsoft for word processing documents, spreadsheets, presentations and charts. The OOXML standard was submitted to the ISO for approval. After initially being rejected over technical concerns, the ISO approved a modified version as ISO/IEC 29500:2008. Microsoft intended to use the OOXML standard for its Office suite. However, Office does not support the standard that the ISO approved, it only supports the standard that was originally rejected by the ISO1. As of Office 2010, Microsoft has still not brought its software into compliance with the standard.
For most purposes OOXML may be considered a subset of DOCX (DOCX contains additional features, like OLE serialization).
Documentation on OOXML may provide a guide to analysing a DOCX file.
Content types
[Content_Types].xml <?xml version="1.0" encoding="UTF-8" standalone="yes"?> <Types ns="http://schemas.openxmlformats.org/package/2006/content-types"> <Default Extension="emf" ContentType="image/x-emf"/> <Default Extension="rels" ContentType="application/vnd.openxmlformats-package.relationships+xml"/> <Default Extension="xml" ContentType="application/xml"/> <Override PartName="/word/document.xml" ContentType="application/vnd.openxmlformats-officedocument.wordprocessingml.document.main+xml"/> <Override PartName="/word/styles.xml" ContentType="application/vnd.openxmlformats-officedocument.wordprocessingml.styles+xml"/> <Override PartName="/word/stylesWithEffects.xml" ContentType="application/vnd.ms-word.stylesWithEffects+xml"/> <Override PartName="/word/settings.xml" ContentType="application/vnd.openxmlformats-officedocument.wordprocessingml.settings+xml"/> <Override PartName="/word/webSettings.xml" ContentType="application/vnd.openxmlformats-officedocument.wordprocessingml.webSettings+xml"/> <Override PartName="/word/fontTable.xml" ContentType="application/vnd.openxmlformats-officedocument.wordprocessingml.fontTable+xml"/> <Override PartName="/word/theme/theme1.xml" ContentType="application/vnd.openxmlformats-officedocument.theme+xml"/> <Override PartName="/docProps/core.xml" ContentType="application/vnd.openxmlformats-package.core-properties+xml"/> <Override PartName="/docProps/app.xml" ContentType="application/vnd.openxmlformats-officedocument.extended-properties+xml"/> </Types> 
Relationships
_rels/.rels <?xml version="1.0" encoding="UTF-8" standalone="yes"?> <Relationships ns="http://schemas.openxmlformats.org/package/2006/relationships"> <Relationship Id="rId3" Type="http://schemas.openxmlformats.org/package/2006/relationships/metadata/core-properties" Target="docProps/core.xml"/> <Relationship Id="rId2" Type="http://schemas.openxmlformats.org/package/2006/relationships/metadata/thumbnail" Target="docProps/thumbnail.emf"/> <Relationship Id="rId1" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/officeDocument" Target="word/document.xml"/> <Relationship Id="rId4" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/extended-properties" Target="docProps/app.xml"/> </Relationships> 
Other relationship files:
word/_rels/document.xml.rels 
Document properties - core
docProps/core.xml <?xml version="1.0" encoding="UTF-8" standalone="yes"?> <cp:coreProperties xmlns:cp="http://schemas.openxmlformats.org/package/2006/metadata/core-properties" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:dcterms="http://purl.org/dc/terms/" xmlns:dcmitype="http://purl.org/dc/dcmitype/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <dc:creator>User 1</dc:creator> <cp:lastModifiedBy>User 2</cp:lastModifiedBy> <cp:revision>3</cp:revision> <dcterms:created xsi:type="dcterms:W3CDTF">2012-11-07T23:29:00Z</dcterms:created> <dcterms:modified xsi:type="dcterms:W3CDTF">2013-08-25T22:18:00Z</dcterms:modified> </cp:coreProperties> 
Document properties - extended: application
docProps/app.xml <?xml version="1.0" encoding="UTF-8" standalone="yes"?> <Properties ns="http://schemas.openxmlformats.org/officeDocument/2006/extended-properties" xmlns:vt="http://schemas.openxmlformats.org/officeDocument/2006/docPropsVTypes"> <Template>Normal.dotm</Template> <TotalTime>1385</TotalTime> <Pages>1</Pages> <Words>2</Words> <Characters>13</Characters> <Application>Microsoft Office Word</Application> <DocSecurity>0</DocSecurity> <Lines>1</Lines> <Paragraphs>1</Paragraphs> <ScaleCrop>false</ScaleCrop> <HeadingPairs> <vt:vector size="2" baseType="variant"> <vt:variant> <vt:lpstr>Title</vt:lpstr> </vt:variant> <vt:variant> <vt:i4>1</vt:i4> </vt:variant> </vt:vector> </HeadingPairs> <TitlesOfParts> <vt:vector size="1" baseType="lpstr"> <vt:lpstr></vt:lpstr> </vt:vector> </TitlesOfParts> <Company></Company> <LinksUpToDate>false</LinksUpToDate> <CharactersWithSpaces>14</CharactersWithSpaces> <SharedDoc>false</SharedDoc> <HyperlinksChanged>false</HyperlinksChanged> <AppVersion>14.0000</AppVersion> </Properties> 
External Links
Introducing the Office (2007) Open XML File Formats, by Microsoft, May 2006
DCMI Metadata Terms
The new XML Office Document Files: Implications For Forensics, Simson L. Garfinkel and James Migletz
Office 2007 Metadata, by Kristinn Guðjónsson, July 10, 2009