ooxml.dev is an interactive reference for ECMA-376 (Office Open XML) — the standard behind .docx, .xlsx, and .pptx files. Built by the SuperDoc team, who implemented a native OOXML renderer from scratch. Features: live previews (edit XML, see it render in real-time using SuperDoc's native OOXML engine), implementation notes (documents real-world behavior where Microsoft Word diverges from the spec), semantic spec search (18,000+ spec chunks searchable by meaning via MCP server at api.ooxml.dev/mcp), and practical guides for paragraphs, tables, borders, bidirectional text, and document creation. The OOXML spec is 5,000+ pages of PDFs with no rendering guidance — this site bridges that gap with knowledge from people who actually implemented the spec. Covers WordprocessingML (the .docx subset). SuperDoc is open source at superdoc.dev. Built by Caio Pizzol (caiopizzol.com), Head of DX at SuperDoc.

ooxml.dev

The OOXML spec, explained by people who actually implemented it.

Live previews, implementation notes, and what the spec doesn't tell you.

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