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Deblunder your chess.

Every mistake has a cause. Deblunder shows you which.

It doesn’t stop at the bad move. It finds out why you keep making the same kind of mistake, turns your games into training and checks whether you’re improving.

Analyze my gamesSee how it works

Chess.com, Lichess or PGN. Just your username. Free diagnosis, no card.

Real game · Rapid · you play Black

The capture wasn’t the mistake.

The e5 bishop was the only piece between the two rooks. Capturing opened the file.

To trainLines a piece blocks

01The cause

An engine says it was a mistake. Deblunder shows why.

The same move, 24...Bxc7, read two ways.

Real game · Rapid · you play Black

Typical analysis

Black’s edge
+8.9+2.0
Best move
Bd4+
Blunder
Blunder

And it stops there. You know you erred, not what you missed.

DeblunderThe cause, linked piece by piece on the board.

02The pattern

One mistake shows what you missed. When it repeats, it shows what you need to train.

Different positions, different pieces, even different colors. Deblunder recognizes when it’s the same mistake.

  1. Game 1you as Black

    You played
    Bxc7
    Line opened
    e-file
    Piece that left
    bishop

    CauseBlocker removed

  2. Game 2you as Black

    You played
    axb5
    Line opened
    a-file
    Piece that left
    pawn

    CauseBlocker removed

  3. Game 3you as White

    You played
    Bxc4
    Line opened
    f5 → b1 diagonal
    Piece that left
    bishop

    CauseBlocker removed

Same cause in 3 gamesIt becomes a pattern and moves up in your training.

Only what repeats across different games becomes a pattern. When a cause can’t be proven, it’s marked unknown.

03Training

Your mistake becomes your training.

The positions where the cause appeared come back to you in sessions of 3, 5 or 10 positions. Each one goes through four steps.

From your game · move 24

Position 2 of 5

You play Black

Black to move. What’s your move?

  • Threats against you
  • Checks and captures
  • The reply to your idea

First attemptBxc7

Only your first try counts. Practicing again never changes your accuracy or your review dates.

04Progress

After training, does the mistake show up less?

Deblunder keeps reading your games and counts how many bring the same cause back. Game by game, not by impression.

Before training

  1. Game 1, with the cause
  2. Game 2
  3. Game 3, with the cause
  4. Game 4, with the cause
  5. Game 5
  6. Game 6, with the cause
  7. Game 7
  8. Game 8, with the cause
  9. Game 9, with the cause
  10. Game 10

6 of 10games with the cause

After training

  1. Game 1
  2. Game 2
  3. Game 3
  4. Game 4
  5. Game 5
  6. Game 6
  7. Game 7
  8. Game 8
  9. Game 9
  10. Game 10

0 of 10games with the cause

The cause appearedGame without it

An observed drop is evidence, not proof that training caused the change. Rating is never promised.

Evidence, not promises

Every conclusion comes from one of your games.

No generic tips. Every cause Deblunder shows points to the game, the move and the position where it happened. You can check every step.

  1. 1Your game

    Rapid · 10 min · you as Black

    1. 23.Na6Rb6
    2. 24.Nc7Bxc7
    3. 25.Rxe8+

    Move 24, Black to play

  2. 2What was verified

    Every fact was checked on the board before becoming a conclusion.

    • The edge dropped+8.9+2.0Confirmed
    • A line openedFrom e1 to e8Confirmed
    • The blocker leftBishop on e5Confirmed
    • The punishment existsRxe8+Confirmed

    Stockfish 18, depth 22

  3. 3The conclusion

    Cause
    Blocker removed
    Skill
    Lines a piece blocks
    Pattern
    3 games
  • No proof, no causeWhat can’t be proven on the board stays unknown.
  • In plain languageExplanations in clear sentences, not engine numbers and codes.
  • No rating promisedYou see progress with the sample in view.
  • Your data is yoursYour history can be exported whenever you like.

Pricing

A coach that studies every game you play.

You keep playing. Deblunder analyzes your new games, finds the cause that weighs most, builds the training and checks whether you improved. Then it starts again with every game.

  1. You playChess.com, Lichess or PGN
  2. It finds the causeAnd the pattern that repeats
  3. You trainWith your own positions
  4. It checksWhether the mistake shows up less

A continuous cycle, fed by your games

Deblunder

Your personal chess coach

Checking price…

Subscribe to Deblunder
  • Secure payment
  • No commitment
  • Cancel in 1 click

Included

  • The cause of each mistake, shown on the position
  • The patterns that repeat in your games
  • New games analyzed on every sync
  • Daily training built from your own positions
  • Spaced reviews at the right moment
  • A check on your progress, with the sample in view

Chess.com, Lichess and PGN · Rapid, Blitz and Bullet · Your history stays yours

Rather try it first? The diagnosis of your games and the first training are free, no card. After that you can still try 7 days of full access and cancel in one click before paying anything.

Start free

FAQ

Before you start.

How is this different from Chess.com or Lichess analysis?

Those analyses show, game by game, which move was better. Deblunder uses an engine too, but goes further: it explains the cause with pieces and lines, looks for the same cause in your other games and turns what repeats into training.

Do I need to pay to try it?

No. Creating the account, connecting your games, seeing the diagnosis and doing the first training are free, no card. After that, you subscribe directly or try 7 days of full access before the first charge.

How does cancelling work?

In one click, in your own account: no commitment, no fee and no one to talk to. On the free trial, cancel before it ends and nothing is charged, and we email you before the first charge. On a subscription, access lasts until the end of the paid period. Your games, diagnoses and training stay saved to view and export.

Do I need to share my account password?

No. Chess.com and Lichess connect through your public username. You can also upload PGN files.

How many games do I need to start?

Preparation analyzes up to 10 games in the time control you choose and can expand to 30. A pattern only appears when the same cause repeats across different games.

What if Deblunder can’t explain a mistake?

It says so. When the cause can’t be proven on the board, the mistake is marked as an unknown cause instead of getting an invented explanation.

How much time does it take each day?

You choose sessions of 3, 5 or 10 positions and set your own routine. You can train in a few minutes between games.

Does it work for Blitz and Bullet?

Yes. Rapid is the default, but you can pick Blitz, Bullet or all of them together. Ratings from different time controls and platforms are never mixed.

Does Deblunder guarantee my rating will go up?

No, and be wary of anyone who does. Deblunder shows whether the causes you train appear less in your next games, with the sample in view. Observation, not a promise.

Can I use it during a game?

No. Deblunder only analyzes finished games, so you train between games.

Deblunder your chess.

Start with your latest games. Find the cause that costs you the most and train exactly that.

Analyze my games

Chess.com, Lichess or PGN. Free to start, no card.

The same position, after training: the e-file shows up before you move.

From analysis to your next better decision.