Stockfish is the strongest chess engine ever created — it plays at a level no human can match — and it's completely free. But most chess players either don't use it at all, or use it incorrectly and walk away confused.
This guide explains what Stockfish is, how it works, and how to use it practically to get better at chess.
What Is Stockfish?
Stockfish is an open-source chess engine that evaluates chess positions and calculates the strongest possible moves. It's been the top-ranked chess engine in the world for much of the past decade and routinely defeats every other engine and every human player.
"Open-source" means anyone can use it, modify it, and distribute it for free. Chess.com, Lichess, and dozens of other platforms run Stockfish under the hood for their analysis tools.
Understanding Stockfish Output
When Stockfish analyzes a position, it outputs several pieces of information:
Evaluation score: A number in pawns indicating who has the advantage. Positive means White is better, negative means Black is better. Read more in our chess engine evaluations guide.
Depth: How many half-moves (plies) ahead Stockfish has calculated. Depth 20 means the engine has looked about 20 moves ahead in the most critical lines. Higher depth = more accurate.
Best move: The single move Stockfish recommends in the current position.
Principal Variation (PV): The sequence of best moves for both sides that Stockfish has calculated. This is the "main line" from the engine's perspective.
Nodes: The number of positions Stockfish evaluated to find its answer. This is a measure of calculation speed.
How to Use Stockfish on Chess.com
- After any game, click "Analysis" at the bottom of the game panel
- Chess.com will run Stockfish through your game automatically
- Blue arrows show the suggested move at each position
- The accuracy percentage tells you how closely each player followed engine-best moves
For deeper analysis, use the "Computer Analysis" feature which runs Stockfish at higher depth.
How to Use Stockfish on Lichess
Lichess offers free Stockfish analysis for all games with no account required:
- Open any game from your history
- Click the computer chip icon (⚙) in the analysis board
- Adjust the depth slider for more thorough analysis
Lichess also has an "Explorer" that shows how your position has been played in thousands of master games — useful for opening preparation.
Stockfish Depth: How Much Is Enough?
| Depth | What it means | Good for |
|---|---|---|
| 10–14 | Fast analysis, misses some tactics | Quick blunder check |
| 15–20 | Standard analysis, good for most positions | Regular game review |
| 20–25 | Deep analysis, finds subtle moves | Complex positions, endgames |
| 25+ | Very deep, slow | Critical positions, opening prep |
For typical post-game analysis at club level (under 2000 Elo), depth 18–20 is more than sufficient. You're unlikely to play moves that only become wrong at depth 25+.
How to Actually Learn From Stockfish (Not Just Watch It)
This is the part most guides skip. Watching Stockfish suggestions is nearly useless unless you engage with them actively.
For every significant move the engine suggests:
- Pause before looking at the continuation. Try to figure out the idea yourself. Why is Nf5 better than Nd4? What does it accomplish?
- Play through the principal variation. Don't just note the first move. Follow the line several moves and understand the resulting position.
- Compare to your actual move. What did you miss? Was it a calculation error, a positional blindspot, or a pattern you haven't seen before?
This active engagement turns Stockfish from a judgment tool into a teacher.
Stockfish in Your Browser With Zero Setup
The traditional way to use Stockfish requires downloading the engine, setting up a GUI like Arena or Chessbase, and loading your games manually. For most players, this is too much friction.
ChessSolve runs Stockfish directly in your browser and overlays its suggestions as arrows on your board while you play on Chess.com or Lichess. You get real-time engine feedback without any installation, configuration, or separate analysis workflow. It's the fastest way to start using Stockfish's analysis during actual games.
Common Mistakes When Using Stockfish
Treating every suggested move as a lesson. Not every engine suggestion is worth studying deeply. Focus on the moves where you diverged significantly (evaluation shift of 0.5+ pawns).
Using Stockfish to prepare specific lines against specific opponents. For most club players, this is wasted time. The opening is rarely why you lose.
Getting demoralized by blunders. Stockfish will find mistakes in every game you've ever played. That's normal. Grandmasters review their games with the engine and see blunders too. The goal is to learn, not to be judged.
Ignoring moves you don't understand. The moves that confuse you are the most valuable ones to study. If Stockfish recommends something and you have no idea why, spend five minutes on it.
Stockfish is the best free tool available for chess improvement. Use it after every game to understand your mistakes, follow the ideas it shows you, and over time you'll internalize the patterns it reveals. Combined with daily tactics and game play, engine analysis is the highest-leverage activity available to any improving chess player.