Describe

Paste formulas, VBA, or describe what you need in plain English. An extensive function library handles common cases instantly.

Iterate

Run and test the generated function instantly in Excel. Refine by continuing the conversation, or download and work locally with the xllify agent for Claude Code.

Deploy

Get a ready-to-run add-in for Excel on Windows, Mac, and the web. Deploy internally or publish on the Marketplace.

What is xllify?

xllify is a platform for creating custom Excel functions. Work directly in an Excel-based authoring environment, or in your favourite editor locally with the xllify agent for Claude Code. Both prioritise verified, tested implementations from the standard library before generating new code. Both produce add-ins powered by the xllify runtime, available for Windows, Mac and Web.

xllify:

Converts messy formulas and VBA into clean, named, reusable functions
Generates actual add-in code that runs locally, your data stays on your machine
Includes a standard library of common functions (regex, joins, lookups, and more)
Runs on Windows (native multi-threaded XLL), Mac and web (WASM)

Multiple runtimes

xllify generates web-based Excel add-ins that run on Windows, Mac and the web. This is Microsoft's modern, cross-platform approach to Excel extensibility, and the default output of xllify.

Additionally, xllify has a native runtime on Windows using the Excel C SDK to build XLL add-ins. XLLs run in-process with Excel and can offer significant advantages over web-based add-ins:

Multi-threaded recalculation - Excel can call your functions across all available cores
Near-zero call overhead - functions execute in-process, not across a web boundary
Self-contained - a single file with no web server or internet connection required
No dependency on a browser runtime or WebView

Both the web and XLL runtimes execute the same bytecode on the same VM, so functions need to be written only once and work identically on every platform, with no subtle differences.

Pricing

xllify is free to use for the creation and packaging of web-based add-ins. Native XLL builds, hosting for web-based Microsoft 365 add-ins, on-premises tooling, and industry-specific function packages are available under a yearly licence, payable monthly or annually. Deployment and distribution, including commercial use, incur no extra costs. Pricing details coming soon.

We are also available for consultancy on Excel add-in development. Get in touch.