What is a .docx file?

Someone sent you a document. It's a DOCX. This is the least surprising sentence in technology because DOCX has been the default Word format since 2007, and Microsoft Word is still how most of the professional world writes things down.

Here's the part most people don't know: a DOCX file is actually a ZIP archive stuffed with XML files, images, and styling data. Rename one to .zip and you can peek inside — you'll find folders like "word/" containing document.xml (your actual text) and various relationship files. The 'x' stands for XML, replacing the older .doc format's proprietary binary blob that only Word could reliably parse. This open structure is why Google Docs, LibreOffice, and dozens of other tools can read and write DOCX without reverse-engineering anything.

Word (subscription, of course) handles DOCX perfectly. Google Docs is free and handles most formatting. LibreOffice Writer is free and does the job for straightforward documents — complex layouts with track changes may get slightly mangled. For sharing a document you don't want edited, convert to PDF with fwip. DOCX became the standard for editable documents the way PDF did for finished ones.