xllify

xllify builds custom function add-ins for Microsoft Excel from prompts or code.

Free to use, from your browser or directly in Excel. Remote builds, no tooling required. Accelerated on Windows.

Describe

Paste formulas, VBA, or describe what you need in plain English. A standard library handles common cases without generating code.

Iterate

Run and test the generated function in Excel or the browser. Refine by continuing the conversation, or work locally with the xllify agent for Claude Code (coming soon).

Deploy

Download an add-in for Excel on Windows, Mac, and the web. Deploy internally or publish on the Marketplace.

No network calls at runtime. Your data stays local. xllify does not depend on a model after authoring. Once built, your add-in is portable and your source code is obfuscated. No external calls, no additional costs. Runs in locked-down environments. The native XLL runtime has no access to the network or file system, thanks to the sandboxed design.

What is xllify?

xllify is a platform for creating custom Excel functions. Describe what you need in a prompt, or write code directly. Work in the browser, in Excel via the xllify Assistant add-in, or locally with the xllify agent (coming soon).

xllify prioritises verified, tested implementations from the standard library before generating new code. The runtime is available for Windows, Mac and Web.

Native XLL runtime

In addition to cross-platform web add-ins, xllify can build native XLL add-ins for Windows. XLLs run in-process with Excel with multi-threaded recalculation, self-contained in a single file with no web server or internet connection required. No local tooling needed: xllify handles everything through a remote build service.

Function code runs in a sandboxed VM with no access to the network or file system, so XLLs built with xllify cannot be used as an attack vector. Both runtimes execute the same bytecode, so functions work identically everywhere.

XLL builds are in preview and available to all users. Builds expire after thirty days.

Remote build service

xllify compiles and packages your add-ins in the cloud. Nothing to install. Write your functions in the browser or in Excel, and xllify produces a ready-to-use add-in in seconds. This applies to both Office Add-ins (WASM) and native XLL builds for Windows. Fair use applies.

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.