JS Visualizer

About

Observe JavaScript execution step by step in real time. Watch animations of the call stack, Web APIs, microtask and task queues, and the event loop. Truly grasp why Promises execute before setTimeout and how async await functions operate. Features include breakpoints, step mode, and speed control. Explore over twenty examples with side by side comparisons and shareable URLs. Each step includes explanations linked to the official specification. It is completely free and requires no registration.