01
Own the document model
DOCX parses into a typed, editable model instead of being flattened into browser markup.
- Semantic import and export
- Byte-identical save of unedited packages
- Unsupported data retained or reported
Open-source DOCX infrastructure
Build documents on an engine you control.
OpenDoc is a deterministic, loss-aware document engine written in Rust. Import,
edit, lay out, render, and write .docx across browser, desktop, and
headless environments — with one authoritative model.
- Apache-2.0
- Rust → WebAssembly
- No required server
Rust coreOne document model
WebAssemblyRuns in the browser
NativemacOS and Windows in CI
HeadlessAutomation and rendering
Loss-awarePreserved or reported
Why OpenDoc
A document runtime, not a web-editor wrapper.
The document itself is the source of truth. The canvas is a rendering surface; UI, storage, authentication, and network policy stay yours.
02
Deterministic layout
One Rust pipeline shapes, paginates, hit-tests, and renders across every host.
- Engine-owned caret and selection geometry
- Tables, sections, columns, floats, math
- Backend-neutral display list
03
Bring your own product
Every edit routes through a closed command set with undo. Everything around it is yours.
- No mandatory UI framework
- No required cloud service
- Browser, native, and headless targets
Architecture
One engine. Clear boundaries.
Document semantics live inside OpenDoc. Product policy lives inside your host. That line is the whole design, so it is drawn rather than described.
OpenDoc core
WebAssemblyNativeHeadless
DOCXpackage + OOXML
Modeltyped document state
Layoutpaginate + hit-test
Pixelsdisplay list
OpenDoc ownsDocument state · transactions · selection · layout · serialization
Your host ownsFiles · fonts · network · auth · telemetry · product UI
Evidence, not promises
Fidelity you can check.
What is supported, how it was measured, and where the gaps still are — including the ones we have not closed.
Page-count parity
Measured 2026-07-27
4 / 5
corpus documents matching LibreOffice's page count exactly; worst delta +2. A manual measurement, not yet a CI gate.
Construct familyRenderedEditable
Paragraphs & textFullFull
TablesPartialFull
Tracked changesPartialPartial
Vertical & rotated textNoneNone
Design principle
Loss-aware
“Preserved or reported — never silently dropped.”
Content the engine does not understand is carried through untouched or named in a compatibility report. Of 27 graded families, 21 round-trip in full.
How they render today
- 7 fully
- 16 partially
- 1 kept, not drawn
- 3 not yet
Developer first
Clone it. Run it. Inspect the engine.
No account, no hosted backend. Every pull request runs the same gates you can run locally.
Putting the editor in your own page has its own guide: Embed the editor.
- Clone the repositoryApache-2.0 and source-first.
- Run the quality gatesBuild, test, lint, docs, and WebAssembly.
- Open a real DOCXIn the browser editor, or embed the runtime.
quickstart
$ git clone https://github.com/CasualOffice/opendoc.git
$ cd opendoc
$ cargo test --workspace --all-features --locked
# run the browser editor locally
$ ./webapp/build.sh
$ ./webapp/serve.pyimport init, { open } from "./pkg/casual_doc_wasm.js";
await init();
const doc = open(new Uint8Array(await file.arrayBuffer()));
// a page-local point (twips, page 1) → a model anchor
const at = doc.hitTest(1, 1440, 1440);
doc.insertText(at.node, at.offset, "Hello from OpenDoc");
const rgba = doc.renderPage(0, 96); // RGBA8888, page 0 at 96 dpi
const docx = doc.exportDocx(); // bytes, ready to save
Delivery
Where it is, and where it is going.
Shipped, active, and planned are kept separate, so a pre-release reads as a status rather than a promise.
Shipped
Loss-aware DOCX
Semantic import and export, and byte-identical save of unedited packages.
Shipped
Deterministic layout
Paragraphs, tables, sections and columns, floats with text wrap, and math.
In progress
Editing to Word parity
Comments, tracked changes, and every editing surface held to the Word and Docs standard.
Planned
Real-time collaboration
Operational transformation over the same transactions, with snapshot and replay versioning.
Not yet: hyphenation · vertical and rotated text · floating tables. Full roadmap
Open a document. Inspect the engine.
No account required for the demo. No opaque hosted backend.