What is a DOCX file?

It is the standard for word processing, but how does it work? Unpack the DOCX file format, its XML structure, and how it compares to PDF.

Large DOCX file icon

What is a DOCX file?

If you have written a document in the last 15 years, you have likely saved it as a .docx file. It is the default file format for Microsoft Word and arguably the most common document format in the world alongside PDF.

But what exactly is a DOCX file? Why did we switch from .doc? And why is it sometimes better (or worse) than a PDF?

The “X” Marks the Spot

The “X” in DOCX stands for XML (Extensible Markup Language). Before 2007, Microsoft Word used .doc, a proprietary binary format. It was hard for other programs to read. In Word 2007, Microsoft introduced Office Open XML. A .docx file is actually a zipped archive. If you rename a file.docx to file.zip and unzip it, you will see a folder full of XML files and images.

Why is DOCX Useful?

  1. Editable: Unlike PDF, DOCX is designed to be edited. Text reflows automatically as you type.
  2. Smaller Size: Because it uses ZIP compression, DOCX files are much smaller than the old DOC files.
  3. Compatibility: Being an open standard, DOCX can be opened by Google Docs, Apple Pages, and LibreOffice, not just Microsoft Word.

DOCX vs. PDF

  • Use DOCX when you are drafting or collaborating. You want the content to be fluid and changeable.
  • Use PDF when you are publishing or sending. You want the layout to be frozen so it looks the same on every screen.

Conclusion

The DOCX format is the workhorse of modern office productivity. Understanding its XML roots helps explain why it is so versatile and why it pairs so perfectly with PDF as the “Draft vs. Final” duo of document formats.

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