Open Document Formula

OpenDocument Formula (also written .odf) is an open, vendor-neutral file format for mathematical equations, standardized as part of ISO/IEC 26300 (the OASIS OpenDocument Format). It's the formula/equation member of the OpenDocument family alongside Open Document Text, Open Document Spreadsheet, Open Document Presentation, Open Document Graphics, and Open Document Database.

Naming note: "ODF" is also the umbrella acronym for the entire OpenDocument Format standard (the family this skill's sibling formats all belong to) — most mentions of "ODF" in the wild refer to that broader standard, not specifically to the .odf formula-document extension. Context disambiguates; this skill covers the file extension.

Package structure

Like every OpenDocument format, an .odf file is a ZIP archive of XML sub-documents:

• mimetype — a plain-text file holding the string application/vnd.oasis.opendocument.formula; it must be the first entry in the ZIP and stored uncompressed, so a reader can identify the format without inflating the whole archive.
• content.xml — the actual equation content.
• meta.xml — metadata (author, creation/modification dates).
• settings.xml — application-specific state.
• META-INF/manifest.xml — an index of every file in the package and its media type.

Content model

Inside content.xml, the equation itself is expressed as MathML — the W3C standard for marking up mathematical notation — rather than a proprietary equation format. This is the format's most distinctive design choice: it defers to an existing open standard for math markup instead of defining its own.

How it's typically used

Unlike .odt/.ods/.odp, a standalone .odf file is relatively uncommon in practice — equations are more often created as embedded objects inside an Open Document Text or Open Document Presentation document (via LibreOffice/OpenOffice Math) than saved and shared as their own top-level file.

Software compatibility

| Category | Software | | --- | --- | | Native/open-source | LibreOffice Math, Apache OpenOffice Math | | Cloud-based | No direct equivalent — Google Workspace's equation editors (in Docs/Slides) don't import or export .odf | | Commercial | Microsoft's Office Math (Word/PowerPoint's built-in equation editor) doesn't natively open .odf; interoperability goes through copy/paste or manual re-entry, not direct format support |

Common pitfalls

• Confusing the acronym with the extension — "ODF" almost always means the whole OpenDocument Format standard in conversation; only the literal .odf file extension refers to this specific formula/equation format.
• Expecting lossless conversion to Word equations — Word's equation editor uses OMML (Office Math Markup Language), a different XML math vocabulary from MathML; equations typically translate visually but aren't a byte-identical round-trip between the two.
• Treating it as a common standalone file type — most real-world math content lives embedded inside a larger odt/ods/odp document, not as an independently shared .odf file.

Learn more

• ISO/IEC 26300 — the international standard defining OpenDocument Format.
• MathML — the W3C math-markup standard ODF formula content is built on.
• Open Document Text, Open Document Spreadsheet, Open Document Presentation, Open Document Graphics, Open Document Database for the other members of the OpenDocument family.