Blog
Thoughts on Excel add-ins, Luau scripting, and building xllify.
Functional extensions for Luau
Higher-order functional primitives now built into xllify
Python in Excel is slow. Here's why XLL functions are faster.
Python in Excel runs behind a service with serialization overhead. XLL functions run inside Excel itself, on multiple threads. Here's what that means in practice.
Excel's fastest custom functions are also the hardest to build. xllify changes that.
XLL add-ins are Excel's highest-performance extension mechanism, but Microsoft say they're impractical for most developers. xllify changes that.
Ever wish you could just add a function to Excel?
Adding a truly custom function to Excel used to mean C++, the XLL SDK, and weeks of work. xllify makes it a few minutes' work.
XLL security: what you need to know
XLLs are powerful but come with a trust model worth understanding before you distribute one.
One codebase, two runtimes
How xllify runs the same Luau function code in both a native XLL and an Office Add-in.
How xllify uses Claude to suggest code
How xllify uses Claude models to generate Luau function code inside the Assistant.
Why xllify uses Luau as its scripting language
Luau is the scripting language behind Roblox. It sounds like a left-field choice for Excel add-ins, but the optimisations that make games fast turn out to benefit spreadsheets too.
Hello, world
Introducing xllify - build Excel custom function add-ins in Luau or with AI code assist, no C++ or JS required.