Engine Analysis

Local Stockfish, cloud engines, analysis modes, and engine output

A chess engine is like having a grandmaster assistant who can analyze any position instantly. It evaluates who's winning, suggests the best moves, and helps you understand why certain positions are strong or weak. Chess.ceo gives you access to Stockfish — the strongest chess engine in the world — running right in your browser.

Getting Started with the Engine

Press E to toggle the engine panel. The engine starts analyzing the current position immediately, updating in real time as you navigate through moves.

You'll see one or more analysis lines appear, each showing the engine's evaluation and its suggested continuation. Don't worry if the numbers seem cryptic at first — the next section explains exactly what they mean.

Understanding Engine Output

Each analysis line displays several pieces of information:

• Evaluation score: How much one side is winning by. Measured in "centipawns" — hundredths of a pawn. An evaluation of +1.00 means White is ahead by roughly one pawn's worth of advantage. -2.50 means Black is ahead by about two and a half pawns. M3 means checkmate in 3 moves.
• Depth: How many moves ahead the engine has calculated. Higher depth means more accurate evaluation — typical depths range from 20 to 40+.
• PV line (Principal Variation): The engine's suggested best continuation for both sides. You can click any move in the PV line to navigate directly to that position.
• NPS (Nodes per second): How fast the engine is calculating — essentially a speed indicator. Higher is better but not something you need to worry about.

Analysis Lines (MultiPV)

By default, the engine shows its top 3 candidate moves simultaneously. Each line represents a different continuation the engine considers strong.

Use the + and − buttons in the engine panel to adjust the number of lines (1–50). Showing just 1 line gives the strongest analysis at greater depth, while showing more lines helps you compare alternatives.

Engine Modes

The engine supports four different analysis modes, each useful in different situations:

Analysis (Default)

Continuous evaluation that updates in real time as you navigate through moves. This is what you'll use most of the time — the engine constantly evaluates whatever position is on the board.

Play

The engine plays one side (you choose White or Black) with approximately 5 seconds per move. Use this to practice positions against a strong opponent or to quickly test whether an idea holds up against best play.

Threat

Shows what your opponent would do if they could move right now. The engine temporarily skips your turn and analyzes the opponent's best response. This is a one-shot analysis — it runs once and stops, so you can study the threats at your leisure.

Lock

Freezes the engine's analysis on the current position. You can navigate freely through other moves while the engine continues to deepen its analysis of the locked position. Useful when you want the engine to keep thinking about a critical moment while you explore what happened next.

WDL (Win/Draw/Loss)

When enabled in settings, the engine also displays Win/Draw/Loss percentages alongside the centipawn evaluation. This translates the raw evaluation into practical winning chances — for example, an evaluation of +1.50 might show as 75% Win / 20% Draw / 5% Loss. This can be more intuitive than centipawns for understanding who's actually winning.

Miniboard Preview

Hover over any move in the engine's PV line to see a small preview board showing what the position would look like after those moves. You can configure the miniboard size in settings.

Local Engine Settings

Stockfish runs entirely in your browser using WebAssembly — no data leaves your computer. You can tune its performance with these settings:

Cloud Engine

For even more powerful analysis, Chess.ceo offers cloud-based engines running on dedicated hardware. This is a subscription feature that gives you access to:

• Stockfish running on powerful CPUs with more threads and hash than your browser can provide
• Lc0 (Leela Chess Zero) — a neural-network engine with a different playing style than Stockfish, running on GPUs

You can provision and manage multiple engine instances, configure threads and hash per instance, and monitor costs in real time. Lc0 instances also offer a contempt slider that adjusts how aggressively the engine plays to win versus playing for draws.

Quick Reference