.docx — Word Document
Document application/vnd.openxmlformats-officedocument.wordprocessingml.document
What a .docx file is
Microsoft Word's format since 2007. Despite appearances it is a ZIP archive containing XML — rename one to .zip and you can look inside.
How to open it
Word, Google Docs, LibreOffice Writer, Pages.
Worth knowing
Complex layouts and tracked changes do not always survive a round trip through a non-Microsoft editor.
How to identify a .docx file
A file's extension is only its name — renaming a.png to a.docx changes nothing inside. What software actually reads is the magic number, the first few bytes of the file.
| Signature | 50 4B 03 04 |
| MIME type | application/vnd.openxmlformats-officedocument.wordprocessingml.document |
| Category | Document |
ASCII "PK" — it is a ZIP archive.
# what is this file really?
file mystery.docx
# look at the first bytes yourself
xxd mystery.docx | head -2
head -c 16 mystery.docx | xxd
# Windows PowerShell
Get-Content mystery.docx -AsByteStream -TotalCount 16 | Format-HexFrequently asked questions
What is a .docx file?
Microsoft Word's format since 2007. Despite appearances it is a ZIP archive containing XML — rename one to .zip and you can look inside.
How do I open a .docx file?
Word, Google Docs, LibreOffice Writer, Pages.
Is .docx safe to open?
Generally yes, though both formats can carry active content — macros in Office documents, JavaScript in PDFs. Modern readers disable these by default; leave it that way for files from strangers.
Can I change a file's extension to convert it?
No. Renaming changes the label, not the bytes. The one place it appears to work is between formats that genuinely share a container — renaming .docx to .zip works because a DOCX is a ZIP. Everything else needs a real converter.