Quick Verdict
Use DOCX when…
Use DOCX for all new documents — it is smaller, safer, and natively supported by Google Docs, LibreOffice, and Pages. It is the universal standard.
Use DOC when…
Use DOC only when you must support Word 97–2003. Otherwise convert all legacy DOC files to DOCX.
DOCX vs DOC: Feature Comparison
| Feature | DOCX | DOC |
|---|---|---|
| Introduced | 2007 (Office Open XML) | 1983 (Binary DOC) |
| File structure | ZIP of XML files (inspectable) | Binary (BIFF/CFB) |
| File size | Smaller by 20–75% | Larger |
| Macro support | Disabled (use DOCM for macros) | Yes (security risk) |
| Track changes | Full, granular | Supported but limited |
| Cross-app compatibility | Excellent — Google Docs, LibreOffice, Pages | Good — some rendering differences |
| Corruption resistance | High (XML is recoverable) | Low (binary corruption is fatal) |
| Maximum features | Full Word 2007+ feature set | Word 2003 feature set |
| ISO standard | ISO/IEC 29500 (OOXML) | Not an open standard |
When DOCX wins
- ✓Introduced: 2007 (Office Open XML)
- ✓File structure: ZIP of XML files (inspectable)
- ✓File size: Smaller by 20–75%
When DOC wins
- ✓Introduced: 1983 (Binary DOC)
- ✓File structure: Binary (BIFF/CFB)
- ✓File size: Larger
Frequently asked questions
Can Word 2003 open DOCX files?
Not without the Microsoft Office Compatibility Pack (a free download). With the pack installed, Word 2003 can open DOCX files but may not render newer formatting elements correctly. For true compatibility, save a .doc copy from a modern Word.
Is DOC more compatible than DOCX?
Counterintuitively, no. DOCX has broader software support today — Google Docs, LibreOffice, Apple Pages, and Dropbox Paper all import/export DOCX natively. DOC requires older compatibility layers and may render differently across apps. DOCX is the de facto standard.
Are macros safer in DOCX?
Yes. DOCX cannot contain macros by design — macros require the .docm extension. This makes DOCX files inherently safer to receive from unknown sources, as they can't run malicious VBA code. Always be cautious with .doc and .docm files from untrusted senders.
How do I convert DOC to DOCX?
In Microsoft Word: open the DOC file, then File → Save As → .docx. In Google Docs: upload the DOC, open it, then File → Download → Microsoft Word (.docx). LibreOffice Writer can also save as DOCX. After converting, check that formatting, tables, and images look correct.
More comparisons
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