File extension
.docx
Office Open XML Document (DOCX)
.docx files are Office Open XML word-processing documents: the modern Microsoft Word format, a ZIP package (OPC) of XML parts and media describing text, formatting, and embedded content.
Known meanings
Formats and reference material for .docx
Office Open XML Document (DOCX)
ZIP-packaged XML word-processing document format (Microsoft Word / ECMA-376 / ISO 29500)
Details
Format notes
Office Open XML Document (DOCX)
DOCX is the default word-processing format of Microsoft Word since Word 2007 and the
successor to the legacy binary .doc. It is part of Office Open XML (OOXML),
standardized as ECMA-376 and ISO/IEC 29500. Despite the similar name, it is
structurally unrelated to the old binary format: where .doc was an opaque OLE
compound file, a .docx is an open, inspectable package of XML.
A DOCX is a ZIP archive following the Open Packaging Conventions (OPC). Inside, the
document text and formatting live primarily in word/document.xml, with related
parts for styles, numbering, fonts, settings, and embedded media (images, objects)
stored as separate files, and a set of .rels files declaring the relationships
between parts. Because it is ZIP-plus-XML, a DOCX can be unzipped and its content
examined or generated by tools without Microsoft Word, which is a major advantage
for automation and interoperability.
Interoperability And Preservation Notes
OOXML is an open standard supported by Word, LibreOffice, Google Docs, and many
libraries, making DOCX a good interchange and preservation format for editable
documents; for long-term archiving, PDF/A is often produced as a fixed-layout
companion. Faithful rendering still depends on available fonts and on how completely
a given application implements the standard. The media type is
application/vnd.openxmlformats-officedocument.wordprocessingml.document.
Security Notes
DOCX can contain VBA macros (as the .docm variant), external references, and
embedded objects, so untrusted documents should be opened with macros disabled and
external content blocked. As a ZIP container, the usual archive precautions apply
(guard against decompression bombs and path traversal when extracting parts).
Further Reading
- Office Open XML overview:
https://en.wikipedia.org/wiki/Office_Open_XML - ISO/IEC 29500 (Office Open XML):
https://www.iso.org/standard/71691.html