Rat

What you write

A working reactive page in eight lines. The same file declares its state, its markup, and the handler that mutates it — no JS to write, no build step, one binary.

> server
name: 'Angelo'
count: 0

> page
<h1> hello [name]
<p> you've clicked [count] times
<button on_click[increment()]> click me

> increment[] >> count << count + 1

What it gives you

• Bracket interpolation — [expr] anywhere a value goes, including attrs and CSS.
• Reactive reads + writes — derived fields with >>, assignments with <<, no manual subscriptions.
• Components (pups) — any .rat in pups/ becomes a tag with attrs as props.
• SSR + DB + handlers — built-in SQLite, function-backed APIs, server-snapshot hydration.

It's fast

Four metrics across three project sizes, median of five runs. The number to look at is hot reload at 1000 pages — the loader's mtime cache reparses only the touched file, so even a project with a thousand pages bounces in 39 ms.

The docs walk through the dialect a piece at a time, with a runnable snippet for every feature. Start with the index or jump to setup.