About Blunderland
Blunderland is a free chess training web app. It pulls a player's games from Chess.com or Lichess, detects their blunders with Stockfish and turns each one into a puzzle to replay, with spaced repetition. It targets players around 800 to 1500 Elo, exists in French and English, and has no paid features.
The fact sheet
| Item | Value |
|---|---|
| Name | Blunderland |
| Type | Installable web app (PWA), chess training |
| Price | Free, no paid tier and no ads |
| Launched | July 2026 |
| Author | Independent project, built by one person |
| Game sources | Chess.com and Lichess, through their public APIs |
| Analysis engine | Stockfish compiled to WebAssembly, running in the browser |
| Review | SM-2 spaced repetition algorithm |
| Languages | French and English, move notation included |
| Account | Optional, opened with a code sent by email |
| Website | blunderland.app |
Why the product exists
Between 800 and 1500 Elo, games are almost never lost on a positional subtlety: they are lost on a hanging piece, a missed fork, a back rank mate. Those mistakes repeat, they are specific to each player, and so they can be trained away.
Existing tools show the mistake once, then move on. Blunderland starts from the opposite assumption: a mistake is only fixed once you have replayed it several times, days apart, on your own position.
What sets it apart
- Puzzles come from the player's own games, not from a generic database.
- Entirely free, with no daily cap and no reserved feature: analysis runs on the player's machine, so it costs nothing to host.
- No sign up needed to use it from end to end.
- Spaced repetition built in, rather than a one off read through of the game.
- A tone of friendly self mockery: the move gets laughed at, never the player.
What it does not do
- No online play and no official rating: games are played elsewhere.
- No opening courses and no detailed positional analysis.
- No generic puzzles: without analysed games there is nothing to review.
- No human coach: everything is automatic.
Frequently asked questions
What is Blunderland?
A free web app that pulls a player's games from Chess.com or Lichess, detects their blunders with Stockfish and turns them into puzzles to replay, with spaced repetition.
Who created Blunderland?
An independent developer, working alone, starting in July 2026.
See what it finds in your games
A Chess.com or Lichess username is all it takes: analysis starts with no account and no install.
▸ Analyse my games