A lightweight component framework with fine-grained signal-based reactivity and single-file components.
Kasper.js is a lightweight framework for building reactive web UIs. It sits between simple templating engines and full frameworks like Vue or React — small enough to understand completely, powerful enough for real applications.
Reactive primitives that update only the exact DOM nodes that depend on them. No virtual DOM, no diffing, no full re-renders.
Write <template>, <script>, and <style> in a single .kasper file. Powered by a Vite plugin with full TypeScript support.
Arrow functions, pipeline operator |>, optional chaining, spread, and more — a proper AST-based expression interpreter, not eval.
@if, @each, @while, @let, @attr, @ref — valid HTML attributes with surgical DOM updates and automatic cleanup.
56KB, zero dependencies, entire API fits in a single context window. Paste llms.txt into any agent and it can write idiomatic Kasper code from scratch.
Written in TypeScript, ships declaration files. Full type checking and autocomplete out of the box.
For more information, visit the official documentation: kasper.top