DOC was the default Word format from Word 97 to Word 2003. Since Word 2007 the default is DOCX, so any .doc you find today is at least 20 years old in its format, even if someone saved it yesterday. The conversion itself is rarely dramatic: both formats describe the same thing, flowing text with styles. The details below tell you what to check afterwards.
Why convert DOC to DOCX
- Uploads: job portals, grant systems and journal submission forms often accept only .docx.
- Co-authoring: simultaneous editing in Microsoft 365, OneDrive or SharePoint works with .docx, not with the Word 97–2003 format.
- Compatibility Mode: Word opens a .doc in Compatibility Mode and switches off newer features until you convert it.
- Safety and mail filters: a .docx cannot contain macros at all (those need .docm), so it raises fewer warnings than an old .doc attachment.
- Size and tools: DOCX is a ZIP archive of XML files, usually smaller, and readable by scripts, search tools and document management systems.
How our converter handles the document
The conversion runs on our servers. It reads the binary DOC (Word 97–2003, and also older Word 6.0 and Word 95 files) and writes DOCX in the Office Open XML format. In detail:
- Kept: text, paragraph and character styles, lists, tables, headers and footers, footnotes, images, hyperlinks, bookmarks, fields such as the table of contents, comments and tracked changes, and document properties like title and author.
- Not kept: VBA macros. DOCX has no place for them by design. If you rely on macros, open the file in Word and save it as .docm.
- Check after conversion: floating text boxes, old WordArt, anchored drawings and complex multi-level numbering. The converter rebuilds the document from scratch, which works for letters, reports and theses but can move an object in an elaborate layout.
- Fonts are referenced by name, as in the original. Nothing is rendered or substituted during the conversion.
Common problems: DOC to DOCX
The layout changed after converting DOC to DOCX
Word lays out a DOCX under its current rules. Microsoft says the same about its own Convert command: it clears the compatibility options, so line and page breaks can move. Compare the page count. If a contract or a thesis must keep exact page numbers, check the cross-references and the table of contents, then update fields (Ctrl+A, F9).
“Microsoft Equation is not available”
Old documents often contain formulas from Equation Editor 3.0. Microsoft removed that editor from all Word versions in the January 2018 update because of security issues, see the Microsoft support note. Our converter tries to turn these objects into editable formulas. Check every equation in the result, and with many formulas convert a sample file first.
Word says the .doc is corrupt or in the wrong format
Many web applications export HTML or RTF and just name the file .doc. Our converter checks the content, not the extension, so such files usually convert fine. A genuinely damaged file may convert only partially, so read the result through.
Password-protected .doc
A document encrypted with a password to open cannot be converted. Open it in Word, remove the password (File, Info, Protect Document, Encrypt with Password, clear the field) and upload that copy.
DOC and DOCX side by side
| DOC | DOCX | |
|---|---|---|
| Default in | Word 97 to Word 2003 | Word 2007 and later |
| Structure | Binary, OLE compound file (starts with bytes D0 CF 11 E0) | ZIP archive with XML parts |
| Specification | Microsoft MS-DOC | ECMA-376 (2006), ISO/IEC 29500 (2008) |
| Macros | Can be inside | Never (macro-enabled variant is .docm) |
The Library of Congress describes both formats in its digital preservation registry: DOC and DOCX. According to the registry, by late 2019 most newly created Word documents were DOCX.
Word can do it too, so when is this converter useful?
For a single file in Word: open it, then File, Info, Convert. Word replaces the .doc with a .docx. Microsoft’s guide Converting documents to a newer format also shows the Save As route, which keeps the original. If you have LibreOffice installed, it can convert a whole folder from the command line: soffice --headless --convert-to docx *.doc.
Our converter saves time when you have no Word licence, work on a phone or a Chromebook, or have an archive of old files: up to 10 files per upload, 100 MB each, and the results come back as one ZIP. Uploads are deleted right after conversion and results after 14 days.
If the document is going to be sent rather than edited, convert it straight to PDF with DOC to PDF or, after the upgrade, DOCX to PDF. Format overviews: DOC, DOCX.