.docx File Extension
.docx file is, which apps open Word documents, how Poly supports them, and when to use PDF, ODT, or another format. File extension details for .docx
Full Support| File type | Microsoft Word Open XML document |
|---|---|
| MIME type | |
| Encoding | Binary ZIP package containing XML and embedded resources |
| Operating systems | Windows, macOS, Linux, iOS, Android |
| Opens with | Microsoft Word, Word for the web, Apple Pages, LibreOffice Writer |
| Poly support | Yes. Poly provides rich document support for DOCX files. |
| Indexed by Poly | Yes. Poly indexes supported text and page content for search. |
| Preview in Poly | Yes. DOCX files have thumbnails and open in a connected document viewer. |
| Poly agent | Yes. The Poly agent can read successfully processed document content. |
What kind of file is a .docx?
A .docx file is a Microsoft Word document stored in the Office Open XML format. It normally uses the application/vnd.openxmlformats-officedocument.wordprocessingml.document MIME type. Microsoft Word uses DOCX as its default document format, and the format cannot store VBA macro code.1
DOCX is a ZIP package rather than one large XML file. Its parts can hold the main text, styles, comments, footnotes, headers, images, and relationships between resources. The first four bytes are commonly 50 4B 03 04, the same ZIP signature used by XLSX, PPTX, EPUB, and ordinary ZIP archives. Reliable identification therefore checks the package contents as well as the filename and leading bytes.2
report.zip, report.doc, or report.docm to report.docx does not convert it. A word processor must open the source and save a valid DOCX package.How do I open a .docx on my computer?
- On Windows and macOS, Microsoft Word provides the most complete editing support.
- In a web browser, Word for the web can open and edit DOCX files, though some desktop features behave differently.3
- On macOS, iPhone, and iPad, Apple Pages can import Word documents.
- On Windows, macOS, and Linux, LibreOffice Writer can open and save DOCX files.4
- On Android and iOS, Microsoft Word and compatible office apps can open them.
If a document uses unusual fonts, equations, revision marks, embedded objects, or complex page layouts, check it visually after opening it in a different application. Interchange is strong, but applications may lay out advanced features differently.
Poly support for .docx
Poly gives DOCX files a first-page thumbnail, a connected in-app document preview, full-text search with OCR support, and page-aware similarity search. Successfully processed content is also available to the Poly agent, which can read and reason about document text and pages.
Preview requires a network connection. Password-protected, damaged, or unsupported documents may not produce the rich preview and content-aware indexing described here.
History of .docx
Microsoft introduced DOCX as the default Word format with Word 2007. The underlying Office Open XML family was standardized as the first edition of ECMA-376 in December 2006 and later became ISO/IEC 29500.15
The move from the older binary .doc format to a documented package of XML parts made it easier for software beyond Word to inspect and produce documents. The same .docx suffix covers both Strict and Transitional conformance classes, so the filename alone does not reveal which class a file uses.2
Working with .docx and alternatives
Choose a format based on what the recipient needs:
| Format | Best for | Main tradeoff |
|---|---|---|
.docx | Continued editing in Word-compatible apps | Layout can vary with fonts and app support |
| Fixed review, printing, and distribution | Harder to edit as a structured document | |
| ODT | OpenDocument editing workflows | Word-specific features may change |
| Plain text or Markdown | Portable, simple text | Loses page layout and rich document features |
Keep the original until you verify a conversion. Check page breaks, fonts, tables, equations, comments, tracked changes, hyperlinks, and embedded objects. Exporting to PDF preserves a review-oriented layout, but it does not preserve the full editable Word structure.6
Footnotes
- Microsoft. XML File Name Extension Reference for Office. Microsoft identifies DOCX as Word's default format and distinguishes it from macro-enabled DOCM. ↩ ↩2
- Internet Assigned Numbers Authority. application/vnd.openxmlformats-officedocument.wordprocessingml.document Media Type Registration. The registration records the suffix, ZIP signature, package model, conformance classes, and security considerations. ↩ ↩2 ↩3
- Microsoft Support. Differences Between Using a Document in the Browser and in Word. ↩
- The Document Foundation. Using Microsoft Office and LibreOffice. ↩
- Ecma International. ECMA-376: Office Open XML File Formats. The archive lists the first edition from December 2006. ↩
- Microsoft Support. Save or Convert to PDF or XPS in Office Desktop Apps. ↩