Frequently asked questions
Everything people ask us about Blunderland, the free chess trainer that turns your blunders into puzzles to drill.
In one sentence
Blunderland pulls your Chess.com or Lichess games, detects your blunders with Stockfish and hands them back as puzzles, with spaced repetition so the correction sticks.
The answers
Is Blunderland free?
Yes, entirely, with no paywall. There is no paid tier at all. Since the analysis runs in your browser, one more player costs us nothing, so there would be nothing to charge for.
Which platforms are supported?
Chess.com and Lichess. Enter your username and the games are fetched through those sites' public APIs. No password is ever requested.
Do I need a Blunderland account?
No. Everything works anonymously, with puzzles stored in your browser. Creating an account, via a code sent by email, only syncs your progress across devices.
Are my games sent to a server?
No. The analysis runs in your browser using Stockfish compiled to WebAssembly. Only fetching the games goes through the public Chess.com and Lichess APIs.
From what level is it useful?
The product targets players from roughly 800 to 1500 Elo, whose games are still decided by tactical mistakes. Above that, blunders become rare and the exercise loses its point.
How does spaced repetition work?
Through the SM-2 algorithm, the one behind flashcards. A puzzle you solve comes back later and later, a puzzle you fail comes back soon. The home screen only shows what is due today.
Can I use it offline?
Yes for reviewing. The site is an installable web app: once added to your home screen, reviewing already generated puzzles works without a network. Fetching new games needs a connection.
Which languages is the site available in?
French and English, move notation included. You can switch language at any time from the account menu.
Ready to own it?
Enter your Chess.com or Lichess username and see what your recent games say about you.
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