opencalc

# OpenCalc [](https://github.com/CasualOffice/opencalc/actions/workflows/ci.yml) [](LICENSE) [](#status) **An Excel-compatible spreadsheet you can run anywhere.** A deterministic Rust engine that reads, calculates and writes `.xlsx`, `.xlsm` and `.ods`, with an editor that looks and works like Excel — ribbon, dialogs, shortcuts, the formula bar — running entirely client-side in WebAssembly. Embed it in a web page, run it as a desktop app, put it behind your file store, or let an AI agent drive it. [**Live demo**](https://calc.casualoffice.org/editor.html) · [Site](https://calc.casualoffice.org) · [Docs](docs/00-README.md) · [Deployment](docs/65-RUNNING-IT.md) · [SDK](sdk/) --- ## Quick start Two containers, and you are co-editing a spreadsheet with someone over a link: ```sh cp .env.example .env # then change OPENCALC_SHARED_SECRET docker compose up --build open http://localhost:8080 ``` New spreadsheet → **Share** → send the link. A cluster (two nodes behind nginx, coordinating through Redis) is `docker compose -f docker-compose.cluster.yml up`. ## Embed it in a web app ```sh npm install @opencalc/sheet ``` ```js import "@opencalc/sheet"; // <opencalc-sheet style="height:600px"> const sheet = document.querySelector("opencalc-sheet"); await sheet.ready; sheet.theme({ light: { accentColor: "#7c3aed" } }); sheet.chrome({ statusbar: false }); sheet.commands({ hidden: ["file.open"] }); await sheet.configure({ access: "view" }); // enforced in the engine, not by await sheet.open(bytes, "budget.xlsx"); // hiding buttons sheet.on("cellsChanged", async (e) => { if (e.source !== "api") persist(await sheet.save()); }); ``` The editor is a custom element with a shadow root, so host CSS cannot reach in and its CSS cannot reach out. The WebAssembly binary is served from *your* origin — a Web Worker cannot be constructed from a cross-origin URL, and a CDN would foreclose ever moving the engine off the main thread. ## Embed it in a Rust host ```rust use casual_calc_sdk::{Environment, SessionConfig, WorkbookSession}; let config = SessionConfig::new() .with_limits(limits) // what an untrusted upload may allocate .with_undo_depth(200) .with_environment(Environment { now: today_serial, seed }); let mut session = WorkbookSession::open_with(bytes, config)?; ``` Time and randomness are **supplied, never sampled**. An engine that reaches for the wall clock cannot be tested, replayed, or agreed on by two hosts. ## Put it in a file store Nextcloud, ownCloud, SharePoint, Moodle and Alfresco all install an editor the same way — WOPI. Start the adapter and paste one URL into their settings: ```sh docker compose --profile wopi up -d # → http://your-host:8090/hosting/discovery ``` Set `OPENCALC_WOPI_ALLOWED_HOSTS` to the file stores you integrate with (it is required), and `OPENCALC_BRAND_NAME` if it should carry your name rather than ours. [docs/74](docs/74-WOPI-INTEGRATION.md). ## What it does **Excel's editor** — Excel's ribbon, File page, dialogs and keyboard (Go To, Find & Replace, Format Cells, Insert Function with argument help, Name Manager, Insert Hyperlink, Paste Special, Goal Seek…), with Excel's message boxes and wording. Merged cells, wrapping, rotated text, frozen panes, row and column autofit, and an expandable formula bar you can resize. Open and save run off the page's thread, so a large file never freezes the grid. **Formats** — `.xlsx` round-trips as a semantic fixed point (gated), and an opened file saved without edits comes back byte for byte. `.xlsm` keeps its VBA project byte for byte. `.ods` reads and writes. CSV/TSV/PSV with RFC 4180 quoting. PDF export embeds subsets of only the glyphs it draws. **Calc** — 494 built-in functions, each with an implementation behind it. Dynamic arrays that spill and refuse (`#SPILL!`) rather than overwrite. `LET` and `LAMBDA` with first-class function values, plus `MAP`/`REDUCE`/`SCAN`/ `BYROW`/`BYCOL`. Automatic or manual mode taken from the file's own `<calcPr>`. **Features** — pivot tables with eleven aggregates and `GETPIVOTDATA`; charts written as real chart parts, not pictures; conditional formatting; data validation; tables and autofilter; notes and comments; hyperlinks to places, defined names and the web; number formats including sections and `[Red]`. **Macros** — JavaScript macros against an ONLYOFFICE-compatible `Api`, stored in the workbook, run in a sandboxed worker as one undo step. Custom worksheet functions through `Api.AddCustomFunction`, with Excel's `#BUSY!` while they compute. A macro reaches the network only after the user allows the site in Excel's Security Notice. VBA is shown read-only (Developer ▸ Visual Basic, Alt+F11) and never run. **Every script** — Japanese, Chinese and Korean render, measure and export with fonts that ship with it and load only when a sheet needs them, with Excel's East Asian font names mapped. Input methods compose straight into a cell. **Collaboration** — server-mediated OT with presence, resume and pipelining. Any node relays to the document's leader, so no sticky sessions and a plain load balancer works. **Agents** — an MCP server (`server/casual-calc-mcp`) lets Claude or any MCP client read and edit workbooks through the same operations the editor uses. [docs/97](docs/97-AGENT-ACCESS.md). **Desktop** — a native app for macOS, Windows and Linux (`desktop/`, Tauri) around the same editor. For what is supported and *how each claim was verified*, see the [execution tracker](docs/14-EXECUTION-TRACKER.md); for where OpenCalc still differs from Excel, and why, see [docs/96](docs/96-EXCEL-FIT-GAP.md). ## Why it is built this way **The engine runs in the browser.** The server orders operations rather than rendering pixels, so a client can be offline briefly without the document freezing, and nodes scale horizontally without consistent hashing. **Nothing is lost silently.** Unmodelled parts of a workbook — VBA, OLE objects, form controls, custom XML — are retained byte-for-byte, and anything the model *cannot* keep is counted and named in a compatibility report rather than dropped quietly. **Determinism is a gated contract.** The same input and version produce identical model, values, layout and bytes, which is what makes regressions testable against golden files. ## Workspace ``` crates/ 16 crates: model, formula, eval, layout, text, import, export, ods, render, sdk, wasm server/ collaboration, WOPI and MCP servers, and a worked-example host webapp/ the browser editor desktop/ the desktop app (Tauri) sdk/ npm packages docs/ design records and the execution tracker ``` Contributor guide: [AGENTS.md](AGENTS.md). ## Status **Alpha.** The engine, editor, desktop app, embeddable SDK and co-editing stack all run, but interfaces still move and the SDK is published at `0.0.0`. Known gaps are tracked in [docs/14](docs/14-EXECUTION-TRACKER.md), and every remaining difference from Excel is listed with its reason in [docs/96](docs/96-EXCEL-FIT-GAP.md). ## License [Apache-2.0](LICENSE). No trademark wall, no mandatory in-product attribution, no separate licence on binaries.