An Excel-style spreadsheet in pure Rust with no telemetry, no subscription, and a permissive license sounds like a weekend demo. GridCraft is not that. It implements 513 of Excel’s 523 worksheet functions, ships as a native app on macOS, Windows, Linux and BSD plus a WebAssembly build, and just released v0.6.1 with about 3.9k stars on GitHub.
It is also, by its own admission, an alpha. The maintainers estimate it is about 50% ready for real work. That honesty is part of why it is worth writing about.
What is actually implemented
The calculation engine is the strong part. It is a dependency graph with incremental recalculation, dynamic arrays with spilling, and the modern function set: LET, LAMBDA, MAP, REDUCE, SCAN, BYROW, BYCOL, MAKEARRAY. Structured table references work. Workbooks are copy-on-write, which makes undo snapshots nearly free.
XLSX is the native format, and round-tripping covers formulas, dynamic arrays, styles, themes, tables, conditional formats, validation, comments, hyperlinks, charts, pictures, sparklines, PivotTables and print settings. CSV and TSV import and export. XLSB and ODS open as saved values. Legacy .xls files open with values and formulas, though formatting and objects are not supported yet.
The gaps are clear: no VBA macros, no Power Query, no .xls fidelity. That alone rules it out for a lot of enterprise workbooks, and the project says so rather than glossing over it. The maintainers publish a parity catalog instead of marketing copy: about 89% of Excel ribbon commands covered, 513 of 523 functions implemented, and an explicit estimate of half-ready for real work. A spreadsheet that admits what it cannot do is easier to trust than one that promises everything.
Clean-room, and why that matters
This is a clean-room reimplementation: workflows and file compatibility are reconstructed from documentation and observation, not from Microsoft’s code. That approach keeps the project legally clear of Microsoft’s licensing and lets it ship under dual MIT or Apache-2.0 licensing while staying file-compatible with the real thing. Clean-room projects of this scale are rare because they are expensive: the team has to rediscover behaviors rather than copy them, which is also why file fidelity improves incrementally instead of overnight.
GridCraft is one project in a family. The ArtCraft team is also building WordCraft (Word), DeckCraft (PowerPoint), PhotoCraft, VectorCraft, PdfCraft and others, all clean-room Rust reimplementations. The Hacker News discussion around the family has been lively, partly because the Office clones follow earlier Adobe-suite clones from the same team. One caution from that thread: stick to the official repo and the getartcraft.com site for facts, because unofficial pages and flagged posts are floating around.
Built for agents, built by agents
Two things make GridCraft more interesting than a Rust curiosity. First, every ribbon button, menu item, dialog, keystroke and mouse gesture is exposed as a command that an external process can invoke, through a JSON control channel, an MCP server, or a headless CLI. That means a spreadsheet can be driven and tested by an AI agent the way a web app is driven by Playwright. The project documents a one-liner to wire it into Claude: claude mcp add gridcraft -- gridcraft-cli mcp.
Second, the project itself is built with heavy AI assistance. Commits carry Claude as a co-author, and the repo maintains AGENTS.md and CLAUDE.md contributor rules for agent-driven development. Whatever you think of that workflow, it is producing 606 commits across 44 contributors on a codebase this size, and the engineering discipline is real: the Cargo workspace enforces layer boundaries, with the egui frontend as a swappable crate so desktop, CLI and web builds all share one engine.
Try it without installing anything
The fastest test is the hosted web build at gridcraft.run, which runs the WASM build entirely in your browser with no upload. If you want the native app, clone the repo and run cargo run --release -p gridcraft (Rust 1.90 or newer), or grab a signed release from the project’s releases page. The honest evaluation method: open your own real workbooks, the messy ones with pivot tables and conditional formatting, and see what survives.
The open question
Spreadsheet clones are a well-worn graveyard. Lotus tried, Gnumeric persists, OnlyOffice and LibreOffice Calc have decades of compat scars. What GridCraft has that its predecessors did not is an agent-first architecture, an engine clean enough to embed in other products, and a maintainership that publishes a parity catalog instead of marketing copy. Whether those advantages survive the long grind of XLSX edge cases is the actual question. The roadmap says XLSX fidelity on real-world files comes next, which is the right next fight. For a daily driver spreadsheet, the honest current answer is: use it alongside Excel, not instead of it, and watch the parity catalog climb.