Interactive Code Execution Visualizer

Interactive Code Visualizer: See How Your Code Really Works

Visualize code execution in real-time. Watch the event loop spin, memory allocate, pointers resolve, and the JVM garbage collect — all step by step.

Open PlaygroundLearn More
playground.js
1console.log("Start");
2setTimeout(() => console.log("Timer"), 0);
3Promise.resolve().then(() => console.log("Promise"));
4console.log("End");
Zero setup required

Step through code instantly.

Watch execution line-by-line. Click run, step through the call stack, and jump straight into the playground.

Execution Preview

Step 1/5
Press Run Visualization to start.
global
Open this exact example in playground
recursion-demo.js

Popular Visualizations

algorithms

Bubble Sort

Compare adjacent elements and repeatedly bubble the largest element to the end.

Run this example

algorithms

Binary Search

Search in a sorted array by halving the search space each step.

Run this example

programming concepts

Event Loop

Microtasks and macrotasks scheduling in JavaScript runtime.

Run this example

programming concepts

Recursion

A function calling itself with smaller inputs.

Run this example

Everything You Need to Understand Code

More than a code runner — a visual learning tool that reveals the hidden mechanics of programming languages.

Multi-Language

JavaScript, Python, C, C++, and Java — all in one playground.

Event Loop Visualization

Watch the JS event loop, microtask queue, and macrotask queue animate in real time.

Memory Layout

See stack vs heap allocation, pointer relationships, and memory lifecycle for C/C++.

Step-by-Step Debugger

Breakpoints, call stack, variable inspection, and line-by-line stepping.

Dark & Light Themes

Beautiful dark and light modes with smooth transitions. Easy on the eyes.

Engine Internals

Python GIL, Java JVM & GC, C++ RAII — see what happens under the hood.

5 Languages, Deep Visualization

Each language has its own engine-specific visualizations

JavaScript Engine

1
Event Loop Animation
2
Call Stack Push/Pop
3
Microtask vs Macrotask Queue
4
Web APIs Tracking
5
Closure & Scope Chain

Try a Data Structure Visualization

See stacks, queues, trees, heaps, and graphs update in real time.

Explore Algorithms

Compare sorting, searching, pathfinding, and dynamic programming flows.

Practice Coding Challenges

Run tests, iterate quickly, and track solved problems.

Explore Code Visualizers

JavaScriptVisualizerPythonVisualizerC++VisualizerJavaVisualizerEvent LoopVisualizerDebuggerVisualizer