About blunder.ninja
What is this?
blunder.ninja is a free, interactive chess opening trainer. No sign-up, no subscription, no ads that track you without consent. Just a board and a sequence of moves to practise until you know them cold.
Think of it as flashcards for chess openings - but instead of flipping cards, you drag pieces on a real board. The trainer checks every move, gives you hints when you are stuck, and celebrates when you nail a perfect line.
Why was it built?
Most chess opening resources fall into two camps: encyclopaedic databases with thousands of lines (overwhelming for casual players) or video courses that are passive to watch. There was no simple, focused tool that lets you practise one line at a time, at your own pace, with zero friction.
blunder.ninja fills that gap. Pick an opening, pick a line, and drill it. That is it. No engine analysis, no opening book, no distractions.
Who is it for?
- Beginners - learn your first openings with clear explanations and bite-sized lines. Start with the Italian Game or Queen's Gambit.
- Club players - build a reliable repertoire without drowning in theory. Focus on the lines that actually happen in your games.
- Anyone preparing for a tournament - drill the critical lines of your repertoire until they are automatic. Set streak goals and track your consistency.
What makes it different?
- Active recall - you play each move from memory, not just read it. This is scientifically proven to build stronger memory than passive study.
- No bloat - 38 openings, 215 carefully curated lines. Quality over quantity.
- Context matters - every opening includes its history, why you should play it, famous practitioners, and classic games. You learn the story behind the moves.
- Privacy first - zero data collection. No accounts. Your progress stays in your browser's local storage. Even the ads require your explicit consent.
- Free forever - no premium tier, no paywall, no "sign up for more lines". Every opening and every feature is available to everyone.
Who built it?
blunder.ninja was built by a solo developer who loves chess but was frustrated by how hard it was to drill openings without getting distracted by engines, databases, and analysis boards. It is open-source and maintained in spare time.
If you find it useful, you can buy a coffee to help cover hosting and domain costs. No pressure - the site will stay free either way.
Have a suggestion?
Missing an opening or a line? Use the Request Opening form (link in the navigation bar) to let me know. Each request is reviewed carefully and added when it fits the collection.