BlunderZero
1
We found what cost the game
Import a game. See the moments that swung the evaluation — explained in plain language.
Your games · Your patterns · Your drills
Turn your own chess mistakes into drills you can master.
Connect Lichess or Chess.com. BlunderZero finds the moments that cost you points, explains the recurring pattern, and creates personal drills from the exact positions you played.
Built for improving online players rated roughly 600 to 1600.
Free unlimited review
On-device Stockfish
No account
Works offline
On a computer?
Scan with your Android phone, or open Google Play on the device where you play chess.
The loop in three screens
Your game → the costly moment → a personal drill. Not random puzzles from someone else’s archive.
2
Here is the recurring pattern
BlunderZero looks across your games for habits that keep showing up, not just one-off blunders.
3
Practise it from your actual position
Train the exact board you reached. Spaced drills until the pattern sticks.
Personal drills beat random puzzles
The engine runs on your phone — so unlimited review is free, private, and offline. The training is built from your mistakes.
♟ On big platforms, full game review is often a premium feature with daily caps.
⚡ On BlunderZero, every imported game gets a full on-device review. Free. No account, no ads, no subscription.
🎯 Generic lessons are made for everyone, from other people’s games.
📈 Your drills come from positions you actually played, with spaced mastery tracking.
Built around your mistakes
Three jobs. Everything else is supporting depth.
1
Find the mistake
Import from Lichess or Chess.com, or paste a PGN. See the moments that cost you points with clear coach explanations.
2
Understand the pattern
Spot recurring habits across games — hanging pieces, missed tactics, king safety — not just a single red move.
3
Master it with personal drills
Retry the positions you reached. Spaced practice until the same mistake stops showing up.
Coaching that speaks your language
Plenty of apps translate their menus. BlunderZero translates the coaching — the plain-language reason a move cost you — into your language, and adds a real-time coach while you play.
Live coach
A coach while you play
Your coach nudges you toward the threat before you move — not only after the game is lost.
Español
The why, in Spanish
“Amenaza de mate…” — the full explanation of the mistake, not just translated buttons.
हिन्दी
In Hindi
“मात की धमकी…” — the same coach explanation, in your language.
Русский
…and Russian
“Угроза мата…” — Stockfish and Maia ideas included, whatever language you read in.
Learn
Learn the ideas behind the mistakes.
When a habit keeps costing you games, drilling the position isn’t always enough — sometimes you need the concept. The Academy teaches the fundamentals in short, cinematic lessons, in the same voice as your coach.
- Guided lessons on the basics that decide club games — hanging pieces, counting attackers and defenders, king safety.
- Taught by your coach, tied to the exact habits your games reveal.
- Bite-sized and visual — a lesson between drills, not a textbook.
Accuracy you can verify
Read the full validation →
We checked our accuracy against Lichess.
We ran 800 player-games through our accuracy code and compared every score against Lichess’s own. Method and public corpus published.
0.978
Correlation with Lichess (Pearson r)
85%
Of games within ±3 points
800
Player-games validated
Public grandmaster sample for method validation — not a claim that your rating band was the corpus. Full details on the validation page.
Also included
Useful depth once the core loop is working — not the product category.
Human-like insight with Maia
See what players at your level often play, beside Stockfish’s best move.
Real-time coach while you play
Feedback in-game so threats are harder to miss before you move.
Opening repertoire tracking
Most-played lines, deviations, and where your prep deserves attention.
Master games lookup
Compare your positions with stronger games when you want context.
On-device Stockfish
Fast, private, offline-first analysis on your phone.
Coach summary & patterns
After a game: what mattered most and which habits keep recurring.
Your games stay on your phone
Chess analysis runs on-device. We do not send your PGNs, moves, or ratings to our servers. Limited pseudonymous analytics and crash diagnostics only — details in the privacy policy.