DOC vs DOCX — What's the Difference and How to Convert

By the Opener team·Updated November 11, 2026·5 min read

A .doc file is the old binary format used by Word 97–2003; a .docx file is the format Word has used since 2007, built from zipped XML. The content can be identical, but many modern tools — including most browser-based viewers — only read .docx. The fix is simple: open the .doc in a word processor and save it as .docx.

What actually differs between .doc and .docx

If you are digging through an old company archive, or an ageing records system just emailed you a .doc, it helps to know what you are holding.

.doc (Word 97–2003) is a binary format. Text, formatting and images are packed together in a structure that was designed around how Word itself worked in the late 1990s. Microsoft eventually published a description of it, but it is complex, full of legacy quirks, and hard for other software to read reliably.

.docx (Word 2007 and later) uses Office Open XML. Under the hood a .docx is a ZIP archive containing XML files: one for the main text, others for styles, headers, footers and comments, plus a folder of images. You can check this yourself — copy a .docx, rename the copy to .zip and open it. Because the format is a documented open standard and made of plain XML, almost any program can parse it, including code running inside a web browser.

The macro row matters for old archives: a .doc can carry macros without any hint in its name, while a .docx cannot contain them at all. That is one more reason to convert files you inherit from unknown sources.

Why many web tools only open .docx

A browser-based viewer has to understand the file without Word installed. With .docx that means unzipping a package and reading XML — well-trodden ground with mature open-source libraries. With .doc it means reverse-engineering a decades-old binary layout, and the results are often unreliable.

That is why Opener’s Word viewer opens .docx only. If you drop a .doc into it, you will see a message asking you to save it as .docx first. Other online viewers make the same trade-off, or they quietly upload your file to a server that runs a full office suite to convert it — something worth avoiding for contracts, HR files or anything personal in that archive.

How to convert .doc to .docx

Any of these produces a normal .docx. Keep the original .doc until you have checked the result.

Microsoft Word (desktop)

Open the .doc. Word shows “Compatibility Mode” next to the file name. Use Save As and choose the Word Document (.docx) type in the file-type list. Word may warn that the layout could change slightly; for ordinary documents it rarely does. Word also offers a Convert option in the Info section of the File menu, which upgrades the document in place.

LibreOffice Writer (free, Windows, Mac, Linux)

Open the .doc in Writer, choose Save As, and pick the Word .docx format from the file-type list. When LibreOffice asks whether to keep the current format, choose the Word format.

For a whole folder of old files, LibreOffice can convert them in one go from the command line:

soffice --headless --convert-to docx *.doc

Run it inside the folder that holds the files; the .docx copies appear next to the originals. On Windows you may need the full path to soffice.exe in the LibreOffice program folder.

Google Docs or Word on the web

Upload the .doc to Google Drive, open it with Google Docs, then download it as a Microsoft Word (.docx) file from the File menu. Word on the web works too: it can open many .doc files and will offer to convert them to the newer format when you want to edit. Both routes upload the file to a cloud account, so keep that in mind for sensitive documents.

Pages on a Mac

Pages opens .doc files and can export them as a Word document, which produces a .docx.

What “Compatibility Mode” means

When current Word opens a .doc (or a .docx created by an older version), it switches to Compatibility Mode. Word limits itself to features the old format can store, so newer layout options, some newer chart types and certain formatting tools are disabled or behave differently. Nothing is wrong with the file — Word is simply making sure that saving it again does not lose anything.

Converting to .docx ends Compatibility Mode. The text stays the same, though complex layouts built with old tricks (manual spacing, unusual tables, old-style text boxes) can shift slightly. For an archive, a quick scroll through each converted document is usually enough.

The same story for Excel and PowerPoint

Excel and PowerPoint went through the same switch at the same time, and the same rules apply.

Convert them the same way: open in Excel, LibreOffice Calc, Google Sheets or Numbers and save as .xlsx; open in PowerPoint, LibreOffice Impress, Google Slides or Keynote and save as .pptx. The LibreOffice command above works with --convert-to xlsx and --convert-to pptx too.

Once converted, they open without any office suite. Opener’s Excel viewer and PowerPoint viewer read .xlsx and .pptx in the browser, and the guides on how to open an .xlsx without Excel and open a .pptx without PowerPoint cover the other options.

Frequently asked questions

Will I lose anything when converting .doc to .docx?

For text, headings, tables and images, almost never. Very old layouts built with manual tricks may shift a little, and any macros are dropped unless you save as .docm. Keep the original until you have checked the copy.

Can I just rename .doc to .docx?

No. Renaming changes only the label, not the contents — the file is still binary inside, and apps expecting .docx will report it as damaged. You need to open and re-save it.

How can I read a .docx without installing Word?

Drop it into the Word viewer: it shows the document with its headings, tables and images, and the file stays on your device. The guide on how to open a .docx without Word lists other free options.

Is .doc still safe to use?

It still opens in Word and LibreOffice, but it is a legacy format and can hide macros. For anything you plan to keep or share, .docx (or PDF for read-only copies) is the better choice.