.docx File — Office Open XML Document

DOCX is the default document format for Microsoft Word starting with Office 2007. It is based on the Office Open XML (OOXML) standard, which was standardized as ECMA-376 and ISO/IEC 29500. Unlike its predecessor DOC, a DOCX file is actually a ZIP archive containing XML files that describe the document structure, styles, content, and metadata, along with any embedded media files. This open format makes it easier for third-party software to read and write Word documents without reverse-engineering proprietary binary structures. DOCX supports rich formatting, themes, styles, headers and footers, footnotes, tables of contents, bibliographies, comments, track changes, and embedded multimedia. The XML structure allows for smaller file sizes through compression and better data recovery when files are corrupted. DOCX has become the most widely used word processing format worldwide.