Play against Stockfish Online

Play against the powerful Stockfish engine online! This is a world-class chess AI.

Stockfish Setup

Think Time: Stockfish has a 1-second think time per move, making for fast-paced games while still playing strong moves.
Opening Play: The engine follows established opening theory from the ECO database. Once out of book, it switches to pure calculation using the Stockfish engine.
Strength: You are playing against the full-strength Stockfish engine, one of the strongest chess engines in the world.
Game Format: Play as White and make the first move. The engine will respond after each of your moves.

Frequently Asked Questions

How strong is this Stockfish engine?

This is the full-strength Stockfish engine, you are playing against. But this online variant only has limited time to think (1 second).

Why does Stockfish sometimes play instantly?

During the opening phase, Stockfish follows established openings from the ECO database. Once the position is out of book, it switches to calculation mode with the 1-second think time.

How this online Stockfish works

This implementation runs the actual Stockfish chess engine directly in your web browser using WebAssembly (WASM) technology. WebAssembly is a low-level binary format that allows code written in languages like C++ to run at near-native performance in web browsers. The Stockfish engine, originally written in C++, is compiled to WebAssembly bytecode and executed as a Web Worker in your browser.

When you load this page, your browser downloads the WebAssembly module containing the complete Stockfish engine. This binary runs in a sandboxed environment within your browser, communicating with the chess interface through the Universal Chess Interface (UCI) protocol. The engine processes chess positions using advanced search algorithms like alpha-beta pruning and sophisticated evaluation functions, calculating millions of positions per second even within the 1-second time limit.

The key advantage of this approach is that all computation happens locally on your device, no chess moves or positions are sent to external servers. This ensures privacy, reduces latency, and provides consistent performance regardless of network conditions. The WebAssembly version delivers the same chess strength as the desktop Stockfish application, making it a truly powerful online chess opponent.