The web, made interactive

Browse 24 interactive simulators, visualizers and playgrounds across 13 web technologies — JavaScript, React, CSS, regex, git, blockchain and more. Every tool runs in the browser — no install, no setup. Just open it and watch the concept come alive.

8 visualizer s 6 playground s 4 simulator s 4 game s 2 interpreter s

13 categories

Choose a technology

JavaScript

Watch the engine run your code — scope chains, the event loop, and execution, step by step.

React

Components, hooks, props, state and the render lifecycle — visualized.

CSS

Play your way to mastery of Flexbox and Grid.

Regex

Build, test and understand regular expressions in real time.

Git

Branch, merge and rebase without fear — visualized as a graph.

Blockchain

Mine blocks, sign transactions and break a chain to see why hashing matters.

Data Structures

Insert, split and rebalance B-trees and more — visualized as you go.

Block Programming

Snap blocks together to learn programming logic — no syntax required.

TypeScript

Type, hover and infer — see what the compiler really knows.

JSX & Babel

See exactly what JSX and modern syntax compile down to.

Sass

Write Sass, see the compiled CSS instantly.

SVG

Understand the path data and coordinate system behind vector graphics.

AST

Turn source code into a syntax tree and explore every node.

Know a simulator we're missing?

The directory grows with the community. Send us the tool and we'll add it.