Convert DOC to DOCX
The jump from .doc to .docx in 2007 was not a version bump. It replaced a binary format nobody outside Microsoft fully understood with a zip archive of XML that anyone can read, and files from the old era are now old enough that opening them at all is becoming a question.
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Up to 50 MB. Deleted automatically after 30 minutes.
What it does
- Text, headings, tables and lists carried across
- Output that opens without a compatibility warning
- Typically about half the size of the original
- No watermark and no sign-up
How to use DOC to DOCX
- 1
Add the .doc
Anything written by Word 97 through 2003, or by the many other programs that wrote the format. Files from a backup, an email archive or a shared drive are the usual sources.
- 2
Convert
The binary document is parsed and its content is written out as OpenXML — the zip-and-XML structure that .docx is.
- 3
Open it and look at the layout
Text almost always survives intact. Page layout is where old documents wander, so scroll through and check that nothing has reflowed onto the wrong page before you rely on it.
How it works
The binary document is parsed by LibreOffice, whose .doc support came from years of reverse engineering before the format was ever documented, and the content is written out as OpenXML.
The two are different enough that this is a genuine translation rather than a re-wrap. Paragraphs, runs, styles, tables and lists all have to be mapped from one model onto another, and the mapping is very good for anything expressed as structure and less certain for anything expressed as position.
What the 2007 break actually changed
Before it, a word processor document was a proprietary binary blob. Interoperating with one meant either licensing the specification or working out the byte layout yourself, which is why competing office suites spent the nineties producing approximations.
After it, the file is a zip. Rename it, unzip it, and you get XML you can read in a text editor, search with ordinary tools, patch with a script, or generate from scratch without any Microsoft code involved.
That is why the format matters beyond Word. Every "export to Word" button in every reporting tool, every document-generation library, every content pipeline exists because .docx is something a program can write. Very few of them could have written a .doc.
Which documents convert cleanly
Built with styles: almost perfectly. If headings are Heading 1 and body text is Normal, the structure maps directly and the result is faithful.
Built by hand: check it. Documents formatted by selecting text and changing the font, with spacing made by pressing Return, carry across as a series of instructions that the new layout engine interprets slightly differently.
Full of embedded objects: expect losses. Charts, equations and pasted spreadsheets from software of that era are the least portable part of any old document.
If the document is finished
Consider PDF instead. If nobody is going to edit it again — a signed contract, an issued report, a piece of correspondence — then what you want is a format that preserves exactly how it looks and does not depend on a word processor at all. Convert to .docx when the document still has a life ahead of it, and to PDF when its life is over and you want the record.
Examples
A memo from a shared drive
Slightly under half the size, which is typical and comes entirely from the container: .docx is a zip, so the XML inside it compresses, while .doc was written to be read directly off a disk with no decompression step. Measured on a real file.
A form built with text boxes and tables
The words and the table structure come through. Precise positioning is the risk: the two formats describe layout differently enough that a document built by nudging things until they looked right will need a look. Documents built with styles convert almost perfectly.
Frequently asked questions
Why bother, if Word still opens .doc files?
It does, in a compatibility mode that disables newer features and warns you every time. More to the point, a lot of other software has stopped: web previews, phone document viewers, collaboration tools and content pipelines increasingly accept OpenXML and nothing else. The support that remains is a courtesy that is being withdrawn gradually rather than a guarantee.
What is actually different about the two formats?
A .doc is a binary compound file — several data streams packed into one structure, holding the text and a great deal of internal state, readable only by software that knows the layout. A .docx is an ordinary zip archive you can unzip: inside are XML files describing the content, the styles and the relationships between them. One was designed to be fast to load, the other to be inspectable and repairable.
What is most likely to go wrong?
Layout in documents built by hand rather than with styles — manual page breaks, text boxes positioned by eye, tables used as a layout grid. Also embedded objects: an old spreadsheet or diagram pasted in as an OLE object may arrive as a static picture or not at all, because the program that created it may no longer exist. Macros are not carried across either.
Should I keep the original file?
Yes, at least until you have read the converted version through. This produces a new file and leaves yours alone, but the check that matters is whether the result is right, and the only way to know is to compare them. For anything with legal or archival weight, keep both.