Blunderbase

Your chess, made clear

See the game.
Find the lesson.

Blunderbase reads your completed Chess.com and Lichess games with Stockfish, marks every move, and turns the mistakes you repeat into practice.

Example insightYour loose pieces were punished in three games.A personal puzzle is ready.
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Completed games onlySeven days of Pro free, no card

  1. 1.e4Book
  2. e5Book
  3. 2.Nf3Book
  4. Nc6Book
  5. 3.Bb5Book
  6. a6Book
  7. 4.d3Blunder

BlunderMissing an opponent threat

Your opponent could win material by capturing your bishop on b5, and your move did not resolve that threat.

Best was Ba4+0.34 → −4.22

Example position, not anyone’s game.

How it works

From your last game to your next puzzle.

Add a username once. Blunderbase does the importing and the analysis; you do the part that makes you better.

  1. Add your username.

    Chess.com, Lichess or both. Blunderbase brings in your completed Rapid and Blitz games: the last ninety days on Free, twelve months on Pro.

  2. Stockfish reads every move.

    Your newest game goes first. On Free the engine runs in your browser while Blunderbase is open; on Pro our server does it, so games are usually ready before you look.

  3. Every move gets a label and a reason.

    Book, Best, Good, Inaccuracy, Mistake, Blunder. Replay at your own pace, try another line on the board, and compare it with the engine’s.

  4. Your mistakes become puzzles.

    The positions where you went wrong come back as personal puzzles, spaced out so the ones you miss return sooner.

New · The coach

One leak at a time.

The coach looks across your analyzed games, names the one mistake that costs you most, and sets a goal you can check: 6 clean games out of your next 10.

  • Counted from your own games, never guessed.
  • Today’s puzzles train that leak.
  • On a mistake, say what happened, and see which answer keeps coming back.
  • On Pro, ask the coach to explain a move: up to 15 answers a day, built from Stockfish’s evidence.
Your leakHanging a pieceMost of the pieces you lost were the one you had just moved.
6clean, of the next 10 games
Goal of 6 met
  1. Game 1: clean
  2. Game 2: the leak again
  3. Game 3: clean
  4. Game 4: clean
  5. Game 5: the leak again
  6. Game 6: clean
  7. Game 7: the leak again
  8. Game 8: clean
  9. Game 9: clean
  10. Game 10: the leak again
What happened, by your own answers
  • I didn’t look at my opponent’s replies7
  • I rushed or was low on time4
  • I didn’t check my line to the end3
  • I looked but missed a piece or square2

Illustrative. Yours is counted from your games.

Beyond your own games

Everything else in the box.

Study other players, drill your own tricks, browse every opening, or watch two AIs fight it out.

Pricing

Most of it is free.

Every new account starts with seven days of Pro. No card, and nothing to cancel.

Free

$0

  • The last ninety days of games
  • Stockfish in your browser, unmetered
  • Every move labeled, with a reason
  • Personal puzzles from your mistakes
  • The coach’s leak and goal, the Notebook, the weekly email
Start free

Pro

$4.99 a month, or $39 a year

  • Twelve months of games
  • Imports every half hour, analyzed on our server
  • A review email after each session, and a monthly report
  • Ask the coach to explain a move
  • Players, puzzle packs and a weekly program
Start with seven days free

Cancel any time; 14 days for a full refund. Full pricing →

Private training, fair play.

Games, mistakes, practice history and reports are readable only by the account that owns them. Blunderbase never assists with an active game. Read what is stored before you import.

Create an account Try the free check