ooxml-core

Read, edit, validate and write Office Open XML documents in TypeScript. One package, one XML model, every format: Word, PowerPoint, Excel and the shared building blocks beneath them. Visio VSDX parsing and bounded editing are available through ooxml-core/visio.

Try the apps  ·  Packages and areas  ·  Install  ·  Examples  ·  Roadmap  ·  Contributing

Why ooxml-core?

• No UI, no framework. Everything runs in browsers, Node.js, Bun, workers and serverless functions. The viewer apps (docx-viewer, pptx-viewer) are thin interfaces on top of it, and so can your application be.
• One package, one structure. All formats share the same XML model, packaging layer, units, colours and geometry. Each format is an area of this one package, not a separate dependency to keep in step.
• Round-trips without losing what it does not understand. Documents are loaded into a model, edited, and written back. Untouched parts stay byte-for-byte, unknown markup is preserved, and edits that would damage unsupported content are rejected instead of silently dropped.
• Strict by default. New code is strict TypeScript with branded measurement units, the shared xml area parses strictly (no DTD or entity expansion), and the docx area is checked against the ECMA-376 schemas in the test suite.
• Honest about its limits. Unsupported features are reported, never hidden, and nothing here claims Office parity or lossless export without evidence.

Features and API: one package, many areas

ooxml-core is a single published package. Every area is a subpath import, so you only load what you use, and the formats are symmetrical: docx, pptx and xlsx are each imported through their own subpaths, and the root entry groups only the shared building blocks by namespace.

import { parseXml } from 'ooxml-core/xml'; // one area
import { xml, opc } from 'ooxml-core'; // or by namespace (shared building blocks)

Area	What it is
xml	The shared XML model: strict DOM parsing and serialization, namespaces, namespace-aware helpers.
opc	Open Packaging Conventions: relationships, content types, part paths, zip helpers, the hyperlink safety policy (hyperlinkPolicy) and document properties (core, app and custom, opc/properties) and digital signatures (signature: detection, the parts a writer strips, XML-DSig parsing and digest checks; the Node verifier is /pptx/signature-node).
units	Branded EMU, twip and point types, constants and conversions.
color	Hex, RGB, HSL and linear colour primitives, OOXML percent and angle parsing.
geometry	DrawingML preset shapes, connection sites, clip paths, callouts and boolean shape operations.
diagram	SmartArt (DiagramML), format-neutral: data model, layout/colour/quick-style parts, the cached dsp:drawing shape tree, relationship resolution and a loader. Used by docx; pptx re-imports its parsers.
digest	Synchronous pure-TypeScript SHA-1, SHA-256, SHA-384 and SHA-512, ECMA-376 digest name normalisation (SHA-512, SHA512, sha_512, ...) and the agile password hash Office protection elements store (hashPassword, verifyPasswordHash). No Web Crypto, so it works on http://. Used by xlsx sheet and workbook protection.
crypto	ECMA-376 package encryption ([MS-OFFCRYPTO]) for every format: decryptOoxmlPackage, encryptOoxmlPackage (agile AES-256/SHA-512 by default, or Standard), isEncryptedOoxmlPackage, and typed errors with a code (password-required, incorrect-password, data-integrity). The compound-file container comes from ole2 (inlined); not in the root entry.
collab	Format-neutral real-time collaboration on Yjs: session and provider lifecycle, awareness/presence, transport-neutral sync (WebSocket, in-memory, any byte channel), update codecs, ordering helpers, asset sync and the product adapter seam. See docs/collab-area.md.
docx	WordprocessingML: model, parser, preserving serializer, editing, validation. Also /docx/embedded. /docx/layout is the DOM-free pagination engine (an approximation of Word, not parity) and /docx/load detects and loads DOCX (also password-protected, { password }) and legacy .doc (ole2 inlined).
pptx	PresentationML: model, parser, serializer, editing, charts, SmartArt, converters, CLI, signatures. Subpaths /pptx/converter, /pptx/cli, /pptx/signature-node.
xlsx	SpreadsheetML: workbook model, .xlsx/.xlsm reader and preserving writer, formula engine (dependency graph, dynamic arrays, 380+ functions), Excel number formats, editing commands with undo, and the DOM-free grid layout (sizes, colours, conditional formats, charts as SVG, drawing anchors). SmartArt is shown from the cached drawing (not re-laid out) and kept verbatim on save. /xlsx/load detects and loads .xlsx, .xlsm (also password-protected: loadWorkbook(bytes, { password }), saveWorkbook(workbook, 'xlsx', { password })), legacy .xls (ole2 inlined) and CSV, and refuses .xlsb with a typed error. Digital signatures are detected and reported, never kept on save. An approximation of Excel, not parity.

Legacy binary formats (.doc, .xls, .ppt) and the compound-file container live in the sibling package ole2; this package never contains binary codecs, and ole2 never contains modern OOXML.

The chart subpath provides shared chart data calculations (regression, quartiles, blank values and stacked series). The text subpath provides script-category segmentation primitives. These areas are DOM-free and do not import a product model. SVG curve flattening is available from geometry. See the PowerPoint reuse audit for extraction evidence and remaining candidates.

Install

npm install ooxml-core

Optional peer dependencies enable specific features: node-forge and xml-crypto for digital signatures (/pptx/signature-node), and @napi-rs/canvas for server-side rasterisation.

Quick start

Open a Word document, change it, save it

import { loadDocx } from 'ooxml-core/docx';

const loaded = await loadDocx(bytes); // Uint8Array | ArrayBuffer
loaded.model.blocks; // paragraphs and tables
const edited = await loaded.save(); // original package parts are preserved

Build or edit a PowerPoint deck

import { PptxHandler } from 'ooxml-core/pptx';

const { handler, data, createSlide } = await PptxHandler.create({ title: 'Quarterly Review' });
data.slides.push(
	createSlide().addText('Hello World', { x: 100, y: 100, width: 600, height: 80 }).build(),
);
const bytes = await handler.save(data.slides); // a valid .pptx

Work at the package level

import { parseXml } from 'ooxml-core/xml';
import { parseRelationships, resolvePartPath } from 'ooxml-core/opc';

const rels = parseRelationships(relsXml);
const part = resolvePartPath('word/document.xml', rels.get('rId5')!.target);

Roadmap

The shared areas come first, then more formats on the same foundation:

• Shared layers: DrawingML (fills, lines, effects, text, theme), charts, diagrams (SmartArt), maths, encryption primitives and schema-generated types, each as an area, written once for every format.
• More formats: Visio (.vsdx, also an OPC package), and further Office Open XML parts as they are needed. Each arrives as its own area.
• One XML model: the pptx area still uses its own XML object model and is compiled with relaxed TypeScript flags while it is migrated onto the shared xml area and tightened. New code is strict.
• Collaboration: the Yjs and sync protocol that the viewers share will live here as a collab area.

Development

You need Bun and Node.js 22 or newer.

bun install
bun run typecheck      # strict project and the pptx project
bun run test
bun run build
bun run test:package   # packs the build and imports every entry point from a clean install

The working agreements are in AGENTS.md, and PROVENANCE.md records where each module came from.

Documentation and related projects

• docx-viewer and pptx-viewer: the editors and viewers built on this package.
• OOXML Office: the suite's launcher page (site/), which opens the demos those viewers deploy to their own GitHub Pages sites.
• ole2: the compound-file container and legacy binary Office codecs.

License

Apache-2.0. Third-party notices are in NOTICE and THIRD-PARTY-LICENSES.