Mission Briefing

Demystifying the Magic.

React is often taught as a set of rules. We believe it should be understood as a system. React Cosmos is a high-fidelity simulator that peels back the UI layer to reveal the deterministic engine of Trees, Linked Lists, and Schedulers underneath.

Accuracy First

All visualizations are derived from the official React Fiber source code. No 'fake' magic—just the actual logic simulated.

Performance Focus

Understand exactly why a component re-renders. We visualize the diffing process so you can optimize with confidence.

Open Education

A community-driven effort to improve React education. Completely frontend-only, transparent, and open-source.

Educational Disclaimer

This is a learning tool. While it simulates internals accurately, it is not the actual React engine running your browser.

System Status

VIRTUAL DOM: ACTIVE

FIBER ENGINE: NOMINAL

CONCURRENT MODE: SIMULATED