DOCX (Microsoft Word Document)
The world's most widely used word processor format, built on open XML standards and readable by virtually every office application today.
| Full name | Microsoft Word Document |
| Extension | .docx |
| MIME type | application/vnd.openxmlformats-officedocument.wordprocessingml.document |
| Developer | Microsoft |
| Released | 2006 (ECMA-376 standard); default in Microsoft Word 2007 (January 2007) |
| Type | Word processor document (Office Open XML) |
| Standard | ECMA-376 (2006), ISO/IEC 29500:2008 |
| Container | ZIP archive of XML files |
What is a DOCX file?
DOCX is the default file format for Microsoft Word documents, introduced in 2007 as part of the Office Open XML (OOXML) standard. It replaced the older binary .doc format and stores content as a collection of XML files inside a ZIP archive. DOCX files are smaller, more portable, and easier to repair than their .doc predecessors.
A DOCX file is a ZIP archive that contains multiple XML files, each responsible for a different aspect of the document. The main document text lives in word/document.xml, while styles, fonts, images, and relationships are stored in separate XML parts within the same package. This modular design means you can open a DOCX file with any ZIP tool and inspect or extract its contents as plain text. The format supports rich text formatting, tables, images, charts, comments, tracked changes, and embedded macros through VBA.
History
Microsoft introduced DOCX in 2006 when it submitted the Office Open XML specification to Ecma International, where it was ratified as ECMA-376 in December 2006. Word 2007 shipped in January 2007 as the first version to use DOCX as its default format, replacing the binary .doc format that had been the standard since Word 97. The specification was later approved by ISO and IEC as ISO/IEC 29500:2008 in November 2008, making DOCX an internationally recognized open standard.
How it works
Internally, a DOCX file is a ZIP package containing a manifest file called [Content_Types].xml that lists every part in the archive. A _rels/.rels file defines relationships between parts, pointing to the main document body at word/document.xml. Character and paragraph formatting is stored in word/styles.xml, while images are embedded as binary files in the word/media/ folder. Each XML part uses the Open Packaging Conventions (OPC) specification, which defines how parts relate to each other and how the package is assembled.
What it is used for
- Writing and sharing reports, letters, proposals, and contracts in a format compatible across Windows, macOS, and Linux
- Collaborating on documents with tracked changes and comments using Microsoft Word or Google Docs
- Converting to PDF for final distribution while keeping the editable source for future updates
- Storing formatted text with embedded images, tables, and charts in a single portable file
How to open it
DOCX files open natively in Microsoft Word (Windows and macOS), LibreOffice Writer, Google Docs, and Apple Pages. On mobile, the Microsoft Word app for iOS and Android handles DOCX files without any conversion.
Pros and cons
Strengths
- Open standard (ISO/IEC 29500) means any application can implement full support
- ZIP + XML structure results in files 25-75% smaller than equivalent .doc binary files
- Human-readable XML internals make it possible to recover content from damaged files
- Supported natively by virtually every word processor and online document service
Trade-offs
- Complex nested XML structure can lead to compatibility differences between applications for advanced formatting
- DOCX files can embed VBA macros, which are a known malware delivery vector
- Large documents with many images or embedded objects can still become unwieldy in size
- Strict and Transitional DOCX variants can cause rendering inconsistencies when switching between editors
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DOCX FAQ
What is the difference between DOC and DOCX?
DOC is the older binary format used by Word 97 through Word 2003. DOCX, introduced in Word 2007, is a ZIP archive of XML files. DOCX files are smaller, easier to repair, and based on an open standard, while DOC files use a proprietary binary encoding.
Can I open a DOCX file without Microsoft Word?
Yes. LibreOffice Writer, Google Docs, WPS Office, Apple Pages, and OnlyOffice all open DOCX files. Basic formatting is reliably preserved; complex layouts with embedded fonts or macros may render slightly differently.
Is DOCX an open format?
Yes. Microsoft submitted the specification to Ecma International in 2006, and it was ratified as ECMA-376. It was later approved as ISO/IEC 29500:2008. The full specification is publicly available, which is why so many applications support it.
Why are DOCX files smaller than DOC files?
DOCX uses ZIP compression on its XML content, whereas DOC stores data in an uncompressed binary format. ZIP compression typically reduces the file size by 25-75% for text-heavy documents, though the difference is smaller for files with many embedded images.