Your games · Your mistakes · Your coach

Stop repeating the
same mistakes.

BlunderZero is a personal chess coach built around the games that matter most: your own. Import your games, find every blunder and missed tactic, and turn them into focused drills.

Free · No ads · No in-app purchases. On-device Stockfish analysis that works offline.

Why BlunderZero?

BlunderZero looks across all your games, finds the mistakes you keep making, and turns them into drills until they stop happening.

✔ Review every move with clear explanations.

✔ Find recurring mistakes and weak habits.

✔ Train on positions from your own games.

✔ Build habits that hold up over the board.

Everything in one coach

From a move-by-move review to drills built from your own blunders.

♟

Personal Game Review

Import PGN games or connect Lichess and get a complete move-by-move breakdown.

🎯

Train From Your Mistakes

Convert your blunders, mistakes, and missed tactics into personalized training drills.

🧠

Human-Like Insight with Maia

See what players at your level would likely play, alongside Stockfish's best move.

🎓

Real-Time Chess Coach

Get clear feedback while you play and learn to spot mistakes before they happen.

🚨

Blunder Detection

Identify the critical moments that changed the game and understand exactly why.

📈

Recurring Mistake Tracking

Discover the patterns that repeatedly appear across your games and focus your training where it matters.

📚

Opening Repertoire Tracking

See your most-played openings, where you deviate, and which lines deserve attention.

🔎

Master Games Lookup

Compare your positions with stronger players and learn from real games.

⚡

On-Device Stockfish

Fast, private, offline-first analysis directly on your phone.

Accuracy you can verify

We checked our accuracy against Lichess.

We ran 800 games through our accuracy code and compared every score against Lichess's own. They line up almost exactly, on a public set of games anyone can pull.

0.978

Correlation with Lichess (Pearson r)

85%

Of games within ±3 points

800

Player-games validated

Read the full validation →

BlunderZero accuracy plotted against Lichess accuracy across 800 player-games; the points hug the perfect-agreement line, r = 0.978.

Each dot is one player's accuracy in one game, plotted against Lichess's own score. The tighter the cloud hugs the diagonal, the closer the match.

How it works

Import or connect

Paste a PGN game or connect your Lichess account.

Review every move

Get clear coach feedback on what went wrong and why.

Train what matters

Drill the mistakes and patterns that cost you most.

Watch weaknesses fade

Build stronger habits and stop losing the same way twice.

See it in action

Coach summaries, move-by-move review, daily drills, and your recurring patterns.