DOCX to Markdown Converter (mammoth.js)
Migrating content from Word to a static-site generator, a wiki, or a docs platform is a recurring task and a chronically annoying one. Word's native XML format (the .docx zip with embedded XML parts) carries a lot of structure that Markdown does not need and a lot of styling that Markdown explicitly drops. The right conversion is structure-preserving and styling-shedding: keep the headings, lists, links, and tables; drop the font, color, and per-paragraph spacing overrides. mammoth.js is the well-tested library for exactly this transform, and this tool runs it in your browser so the document never leaves the tab.
What mammoth.js Preserves
Headings (Heading 1 through Heading 6 styles in Word map to # through ###### in Markdown), paragraphs, ordered and unordered lists (with nesting), hyperlinks, inline bold and italic, and inline code formatted with the Code character style or with a monospaced font. Basic tables are preserved as GitHub-flavored Markdown tables when they have a single header row and no merged cells. Images are extracted from the .docx and embedded inline as data URIs by default; an option re-emits them as external references if you want to handle the images separately in the destination platform.
What mammoth.js Drops
Direct character formatting beyond bold/italic/code (font family, font size, color, highlight) — these have no Markdown equivalent and are intentionally dropped. Page-level constructs (headers, footers, page numbers, page breaks, multi-column layouts) — same reason. Tracked changes and comments — the rendered output is the accepted, comment-free version; the tracked-changes history is not part of the Markdown output. Equations rendered with the Word equation editor become a placeholder; for documents with serious mathematical content, a dedicated Word-to-LaTeX or Word-to-MathML tool is a better fit.
Before you convert, take a look at who authored the file and when — the DOCX Metadata Inspector reads the core, app, and custom properties from a .docx in your browser.
Why a Custom Style Map Is Sometimes Worth It
mammoth.js uses a style-map system that lets you specify how named Word styles convert to Markdown. The default map covers all the standard Heading and List styles. For documents that use custom styles (a corporate template often has a "Callout" style or a "Code Block" style that the default map doesn't recognize), you can provide a custom map at conversion time. The tool exposes the standard map by default and an advanced panel for entering a custom style-map string — the same syntax mammoth.js accepts in its programmatic API. Most users never need this; for a one-off migration of a heavily-templated corpus it can be the difference between a clean output and one that needs hours of post-processing.
Browser-Only Conversion and the Privacy Posture
The whole conversion happens locally. mammoth.js is bundled into the page (about 493KB minified, loaded on demand the first time you convert a file). When you drop a .docx file in, it is read into a browser Blob via FileReader, parsed by mammoth.js as a zip archive, walked as XML, transformed to Markdown via the style map, and offered as a download. Nothing crosses the network. This matters for any document that contains internal information — personnel records, legal drafts, financial reports — where uploading the file to a server-side converter would be a small but real disclosure risk. The Network tab in your browser confirms no upload occurs.
Pair this with the rest of the UDT document-conversion cluster: DOCX Metadata Inspector for examining author, dates, and document properties before or after conversion, PDF to DOCX for the upstream PDF case, Markdown Preview for previewing the converted output, and HTML to Markdown for the HTML-source case.
Frequently Asked Questions
Built by Derek Giordano · Part of Ultimate Design Tools