A free chess game analyzer that actually explains your mistakes

Most analyzers flag a move red and show you a number. That tells you that you blundered — never why. Here's how to get the explanation that actually makes you better, free.

You finish a game, click "analyze," and the engine lights up your move in red: Blunder. −4.2. An arrow points at the move you "should" have played. And then… nothing. You stare at it. You half-understand. You close the tab and go play the next game — where you make the exact same kind of mistake again.

This is the quiet flaw in almost every free chess analyzer. There are dozens of them, and most are genuinely good at the engine part: they run Stockfish, grade every move from Brilliant down to Blunder, and give you an accuracy percentage. But a centipawn score isn't coaching. Knowing you dropped from +1.2 to −2.4 teaches you nothing if you don't understand the idea you missed.

What "explains your mistakes" should actually mean

A real coach sitting next to you wouldn't just say "that's a blunder." They'd say: here's the trap you fell for, here's why it worked, and here's the question to ask yourself next time so it never happens again. That gap — between knowing a move was bad and understanding why — is exactly where improvement happens.

Here's the difference in practice. Imagine you grabbed a free queen with 5...Bxd1 and got mated a few moves later.

Notice what just happened. You didn't get a number — you got the name of the trap, the reason it worked, the better move, and a thinking habit you can carry into your next game. That's the standard a chess analyzer should be held to.

How postgame analyzes a game

postgame pairs the two halves you actually need: the strongest open-source engine and a coach who can talk.

• Stockfish finds the truth. Every position is evaluated by one of the strongest engines in the world, so the turning points are real, not guessed.
• Claude explains it like a human. The engine's findings are translated into plain-language coaching — what you missed, why it mattered, and what to do next.
• It remembers you. The more games you review, the more it sees your recurring mistakes across games — the patterns no single-game review can catch — and gives you one clear priority to work on.

How to analyze your first game (about two minutes)

• Enter your Chess.com or Lichess username and pick a recent loss — or paste any PGN.
• Choose a quick review (1 credit) or a deeper move-by-move review (2 credits). You start with 3 free.
• Read the report: each critical moment is explained, with the concept you missed named and a tip to remember.
• Replay the game on the interactive board, with the engine's best line and your coach's notes side by side.

Free engine vs. a coach that explains: which do you need?

If all you want is to confirm a move was bad, any free Stockfish tool will do — and several offer unlimited analysis. But if you keep losing the same way and you don't know why, raw engine output is the wrong tool. You don't need more numbers. You need someone to tell you what the numbers mean and what to practice. That's the job postgame is built for.

Start free, analyze a couple of your recent losses, and see whether "the whole story" beats "−4.2." Your first three are on us.