What is the DOCX file format?
Files with the .docx extension contain formatted text documents, possibly with graphic elements, stored in a format native to Microsoft Word and introduced with Word 2007. .docx files are part of the Office Open XML (OOXML) specification, standardized as ISO/IEC 29500. Each .docx file is compressed using the ZIP archive method and built on XML, using the markup languages WordprocessingML and DrawingML, developed by Microsoft.
.docx is the successor of the proprietary binary format .doc. It offers better portability across programs and platforms thanks to its open specification. .docx does not support macros - to enable macro use, a file must be saved in the .docm format instead. Most office suite applications support .docx, and files can be converted to other formats such as .odt.
.docx files are so widely used that virtually every advanced word processor supports them. Beyond dedicated desktop software, .docx files can be opened and edited for free in online editors such as Google Docs and Word for the web. These web editors closely resemble their desktop counterparts, making them accessible to most users without any additional software.
Security & safety
RISK: LOWPlain DOCX cannot run macros, which makes it safer than the older .doc or the macro-enabled .docm: a normal .docx is essentially a container of text and images. The residual risks are (1) macro-enabled documents disguised by extension - a real .docm or a renamed file can carry VBA macro malware, so never click 'Enable Content' on a document you didn't expect; and (2) embedded links/objects and template injection. Modern Office opens documents from e-mail/the internet in Protected View. Opening an unknown DOCX in Google Docs or LibreOffice is generally safe because the text renders without executing Word VBA.
Format details
in a nutshellFULL NAMEMicrosoft Word Open XML Document
DEVELOPERMicrosoftsince 2007 (Word 2007 / Office Open XML); ISO/IEC 29500 in 2008
CATEGORYText Files
MIME TYPEapplication/vnd.openxmlformats-officedocument.wordprocessingml.document
TYPEZIP-based Office Open XML package (zipped XML)
STANDARDOpen · royalty-free
MAGIC BYTES · FILE SIGNATURE
OFFSET
00010203
HEX
504B0304
ASCII
PK··
A DOCX is a ZIP archive, so it starts with "PK" (50 4B 03 04) like any ZIP. It is distinguished from a plain ZIP by its internal structure: [Content_Types].xml plus a word/document.xml part. This is unlike the older .doc, which is an OLE2 binary starting with D0 CF 11 E0.
Programs that open DOCX files
Windows3 apps
Microsoft Word
Paid The native editor; double-click to open and edit. Word is the highest-fidelity option. 
LibreOffice Writer
Open-source Free, full-featured. Double-click to open; File > Save As to keep DOCX or export to PDF. 
WPS Office Writer
Freemium Free Word-like editor (formerly Kingsoft); opens and edits DOCX with a familiar ribbon UI. 
macOS3 apps
Apple Pages
Free Free on Mac; File > Open imports the DOCX, and File > Export To > Word saves back to DOCX. 
Linux1 app
LibreOffice Writer
Open-source Pre-installed on most distros; double-click to open and edit DOCX, save back as DOCX/PDF. 
Android3 apps
Microsoft Word (mobile)
Freemium Tap the file to view/edit; basic editing is free on small-screen devices.
iOS1 app
Web2 apps
Word for the web
Free Upload the DOCX to OneDrive and open in Word online (free Microsoft account) - highest compatibility online. Technical details
deep spec| Container format | ZIP-based OPC (Open Packaging Conventions) archive - compatible with any standard ZIP tool |
| Primary markup language | WordprocessingML XML (namespace prefix w:), defined in ISO/IEC 29500 Part 1 |
| Graphics markup language | DrawingML, shared across Office Open XML formats (.docx, .xlsx, .pptx) |
| MIME type | application/vnd.openxmlformats-officedocument.wordprocessingml.document |
| Magic bytes | 50 4B 03 04 ("PK") at offset 0 - standard ZIP local-file header; distinguished from plain ZIP by internal structure |
| Main document part | word/document.xml - contains the entire document body (paragraphs, tables, runs) |
| Package manifest | [Content_Types].xml at archive root - declares MIME types for every part in the package |
| Macro support | None; macros are prohibited - macro-enabled documents use the .docm extension instead |
| Style definitions | Paragraph and character styles stored in word/styles.xml, applied via w:pStyle and w:rStyle attributes |
| Image storage | Binary media files kept under word/media/, referenced via OPC relationship files in word/_rels/ |
| Tracked changes | Stored inline as <w:ins> (insertion) and <w:del> (deletion) XML elements within the document part |
| Theme storage | Color palette, font scheme, and visual effects defined in word/theme/theme1.xml |
| Footnotes and endnotes | Stored as separate package parts: word/footnotes.xml and word/endnotes.xml, linked via relationships |
| Headers and footers | Each section's header/footer stored in independent parts (word/header1.xml, word/footer1.xml) |
| Character encoding | UTF-8 for all XML parts within the package |
| Released | 2007 (Word 2007 / Office Open XML); ISO/IEC 29500 in 2008 |
| Open standard | Yes · royalty-free |
| Specification | learn.microsoft.com |
DOCX conversions
Possible
.DOCX .ZIPGUIDE
A DOCX file is already a ZIP archive, so the fastest way to "convert" it is to copy the file and rename the…
How to convert
.DOCX .HTMLGUIDE
Yes - open the document in Word, LibreOffice Writer, or Google Docs and save it as a web page (HTML) in one…
How to convert
.DOCX .PDFGUIDE
Yes -- open the DOCX in Microsoft Word, LibreOffice Writer or Google Docs and use File > Export (or Download…
How to convert
.DOCX .TXTGUIDE
Yes -- open the DOCX in any word processor and use Save As to save it as plain text (.txt); the fastest route…
How to convert
.DOCX .DOCGUIDE
Yes, DOCX converts to DOC -- the fastest way is File > Save As > Word 97-2003 Document (.doc) in Microsoft…
How to convert
.DOCX .ODTGUIDE
Yes - open the file in LibreOffice Writer and use File > Save As > ODF Text Document (.odt), which takes…
How to convert
.DOCX .RTFGUIDE
Yes - open the DOCX in Word or LibreOffice Writer and use File > Save As > Rich Text Format (.rtf) in one…
How to convert
.DOCX .JPGGUIDE
Yes -- the fastest route is to export the DOCX to PDF first, then convert the PDF pages to JPG using…
How to convert
Community Q&A
asked by users
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Frequently asked questions
How do I open a DOCX file without Microsoft Word?
Use the free LibreOffice Writer (Windows/Mac/Linux), upload it to Google Docs, or open it in Word for the web - all free. On a Mac, Apple Pages opens DOCX too.
What is the difference between DOC and DOCX?
DOC is the older Word 97-2003 binary format; DOCX (since Word 2007) is a ZIP+XML format that is smaller, more robust, and an open standard. Any modern word processor reads both.
How do I convert a DOCX to PDF?
Open it in Word, LibreOffice Writer or Google Docs and choose Save As / Export / Download as PDF. This creates a fixed, non-editable copy that looks the same everywhere.
Can I open a DOCX on my phone?
Yes. Install Microsoft Word, WPS Office or Google Docs on Android, or use Pages/Word on iPhone/iPad. Basic editing is free on phones.
Can Google Docs open a DOCX file?
Yes. Upload the file to Google Drive and open it with Google Docs; you can edit it and download it back as DOCX or PDF.
Why does my DOCX look slightly different in LibreOffice or Google Docs?
Some Word features (certain fonts, advanced layout) are application-specific, so complex documents can shift a little in other apps. For exact fidelity use Microsoft Word, or share as PDF.
Is a DOCX file safe to open?
A plain .docx can't run macros, so it's generally safe. Be cautious only with macro-enabled .docm files or unexpected attachments - never click 'Enable Content' on a document you didn't request.
References
1ISO/IEC 29500 - Office Open XML File Formatswww.iso.org
2Microsoft - [MS-DOCX] Word Extensions to the Office Open XML formatlearn.microsoft.com
