IronCalc

IronCalc is a spreadsheet engine built for developers and product teams who need spreadsheet functionality without depending on Excel, Google Sheets, or any third-party service. It's not a hosted SaaS product. It's an embeddable, self-hostable engine you control entirely.

Built in Rust and compiled to WebAssembly, it runs fast in the browser with no accounts required. The core is MIT/Apache 2.0 licensed, backed by the European Commission's Horizon Europe programme and the NLnet Foundation.

What it can do today:

• 300+ functions with Excel-compatible behavior and LET/LAMBDA support
• .xlsx import and export, preserving formulas and formatting
• Rich and conditional formatting, named ranges, dynamic arrays, multiple sheets
• Python and JavaScript bindings for server-side or headless use cases
• Multi-language and multi-locale support with timezone handling
• Autofill, frozen rows/cols, image upload, custom formats, and templates

There are four main ways people use it. As an everyday spreadsheet for budgets and planning. As a professional tool for forecasts and scenario modeling. As an embedded engine inside SaaS products or dashboards. Or headlessly, running formula logic and business rules programmatically on a server.

Compared to tools like LibreOffice or Collabora Online, IronCalc isn't trying to be a full office suite. It's focused on the engine itself, which makes it a better fit when you want to add spreadsheet logic to an existing product rather than replace a desktop app.

Real-time collaboration and charts aren't supported yet. The project is pre-1.0 and actively evolving, but it's usable now. Browser storage handles persistence in the web app; server-side storage is left to your integration.

If you're building a tool like Grist or need spreadsheet capabilities inside a product like Teable, IronCalc gives you a clean, dependency-light foundation to build on.