Free · No signup · No daily review limit
Stuck at the same rating? See the 3 mistakes you keep repeating.
Enter your Chess.com username (Lichess works too). BlunderLens reads your own recent games, runs Stockfish on them right in your browser and shows the 3 mistakes you keep making, with a plain-English why, a fix and a drill for each. Free, with no daily review limit.
How it works
Stop guessing what to study
Puzzles, slower games, "analyse your games": you know the advice. BlunderLens does the tedious part, game after game, in about a minute.
Enter your username
We fetch your most recent public games through the official Chess.com (or Lichess) public API. No login, no PGN files.
Stockfish checks every move
The engine runs on your own device and measures how much each move changed your winning chances.
Fix your top 3 patterns
Errors are grouped across games and ranked. Each one comes with example positions, a concrete fix and a drill.
Sample report
What you get, on real games
This is the top of a real report for a public Chess.com account (Erik Allebest, Chess.com co-founder). Yours looks the same, built from your own games.
What we look for
Patterns across games, not one bad move
Single-game reviews tell you what went wrong in that game. BlunderLens asks what keeps happening.
Blunders by phase
Do you lose games in the opening, the middlegame or the endgame? We count it.
Missed chances
Moments when your opponent blundered and you didn't punish it.
Thrown wins
Winning positions that ended in a draw or a loss.
Openings & clock
Your worst-scoring openings by colour and how many losses come from time trouble.
Free vs. paid
The report is free. The plan is optional.
Use the free report as often as you like. If you want help turning it into practice, the Daily Training Plan does that.
Free report
Find out what's holding you back.
- Last 12–20 games checked by Stockfish
- Up to 60 recent games for opening & clock stats
- Your top 3 repeated mistakes, ranked
- Example positions with the better move
- A fix and a drill for each mistake
- A share image for your club or friends
Daily Training Plan
Everything in the free report, plus a routine to fix it.
- A short daily plan built from your own games
- Positions you got wrong, turned into exercises
- Opening fixes for the lines that cost you points
- By email · cancel anytime yourself
Early access: we prepare the first plans ourselves, so your first plan arrives by email within 48 hours of signing up. Full refund if you ask within 14 days of your first payment.
FAQ
Questions
Is the report really free?
Yes. The engine runs on your device, so a report costs us nothing to run. No account, email or password is needed, and you can run it as often as you like.
How is this different from Chess.com Game Review?
Game Review looks at one game at a time. BlunderLens looks across your last 12–20 games and counts what repeats: where you blunder (opening, middlegame, endgame), opponent blunders you didn't punish, winning positions you let slip, losses on time and your worst-scoring openings. Then it ranks the top 3 so you know what to work on first.
I already do puzzles and watch videos. Why am I still stuck?
Generic puzzles and videos train generic skills. If most of your lost points come from one habit, for example missing your opponent's threats in the middlegame or losing on the clock, that habit stays until you train it on purpose. The report tells you which habit it is, using your own games.
Does it tell me why a move was bad, or just the best move?
Each pattern comes with an explanation, a concrete fix (for example a blunder check before each move) and a drill, plus links to the exact games and positions. Stockfish shows the better move; the report focuses on the habit behind the mistake.
Does it work if I'm a beginner or only play blitz or bullet?
Yes. It uses your recent rapid, blitz, bullet and daily games. Patterns like hanging pieces, missed chances and time trouble show up at every rating. Faster games are noisier, so treat single moves as hints and look at the patterns.
How accurate is it?
We use Stockfish 17 at a moderate depth so the report finishes in about a minute. The patterns are reliable; individual moves should be treated as hints. Choose "Deeper" for more accuracy.
Will it slow down my phone? Do you store my games?
The analysis uses your device's processor for about 30 seconds (Quick) or 2 minutes (Deeper); on older phones it can take longer. We don't store your games or your report. The engine runs locally and only public game data is fetched.
Is BlunderLens part of Chess.com?
No. BlunderLens is an independent tool and is not affiliated with Chess.com. It only reads the public game data that Chess.com makes available through its public API.
Does it work for Lichess?
Yes. Pick "Lichess" above the username box. We read your recent public Lichess games (with clock times) through the official Lichess API, exactly like we do for Chess.com.
What exactly do I get with the Daily Training Plan?
A short daily routine by email, built from your own games: positions you got wrong turned into exercises, drills for your top patterns and fixes for the openings that cost you points. It's in early access, so we prepare the first plans ourselves and send the first one within 48 hours.
Can I cancel the Daily Training Plan? Can I get a refund?
Cancel anytime, yourself, in the subscription portal (log in with the email you paid with), or email us and we'll cancel immediately. If you're not happy, email us within 14 days of your first payment for a full refund. Payments are processed securely by Stripe.
Get one practical chess tip a week
Plus news when new reports launch. No spam, unsubscribe anytime.