Opening Stats: which openings are actually costing you rating
Most players have a rough feeling for this — "I think I do badly against the Sicilian" — but no actual number. Opening Stats builds the number, straight from every game you've imported from chess.com and lichess.org.
It groups your games by opening family and by which color you played, scores each group by standard chess scoring (a draw counts half), and sorts best to worst. Openings you've barely played still show up for reference, but only ones with a real sample size get picked out as your single best and single worst — so a fluke 1-0 in an offbeat line never gets mistaken for a pattern.
Opening Coach: a repertoire trainer that plays like a real opponent
Pick a repertoire, and the coach takes the other side — varying between its important tries the way a real opponent would, weighted like an opening book rather than always playing the same line. Your job is to find the repertoire reply to whatever it actually plays.
Wrong replies are taken back immediately, with feedback — targeted ("4...Bh5? runs into 5.exd5!...") wherever the catalog has authored that specific mistake, or a gentle nudge toward Hint otherwise. A two-step Hint shows the piece to move first, then the destination, so there's still a chance to work it out yourself. Finished lines count toward covering the whole repertoire tree, and a specific named variation can be targeted directly from the setup screen instead of leaving it to chance.
Engine territory: what happens after the book runs out
Every repertoire line eventually reaches the edge of prepared theory — usually 8 or 9 moves deep. Older opening trainers just stop there. ChessMend keeps going: the moment you're past the last authored move, Stockfish takes over both sides at full search strength, and the board shifts to a distinct teal-green so it's always obvious you've left the book.
Hint and Play-it-for-me both ask the engine from here on
Once in engine territory, Hint and Play it for me stop consulting the repertoire tree — there's nothing left in it — and ask Stockfish for its own top move instead, at the same search depth ChessMend's strongest bots use. Any legal move you play is accepted; there's no more "book" move to be right or wrong about, just a continuing, engine-verified game from the position your prep left off.
The repertoire library
Sixteen hand-built repertoires ship with ChessMend today, evenly split between White and Black, each carrying named variations and running to around move 8-9 before handing off to the engine. Every line is verified move-by-move for legality before it ships. The library grows with every release — see the What's new page for the latest additions.
| Repertoire | ECO | Color |
|---|---|---|
| Italian Game | C50–C54 | White |
| Scotch Game | C45 | White |
| Vienna Game | C25 | White |
| King's Gambit | C30 | White |
| Queen's Gambit | D06–D69 | White |
| London System | D02 | White |
| English Opening | A10–A29 | White |
| King's Indian Attack | A07–A08 | White |
| Caro-Kann Defense | B10–B19 | Black |
| Caro-Kann: Meeting the Advance Variation | B12–B13 | Black |
| Sicilian Defense (Najdorf) | B20–B99 | Black |
| King's Indian Defence (vs 1.d4) | E60–E99 | Black |
| Réti Opening, Flexible Indian Setup | A04–A09 | Black |
| Réti Opening, Solid Center | A04–A13 | Black |
| Alekhine's Defense | B02 | Black |
| Petrov's Defense (Russian Game) | C42 | Black |
Réti and King's Indian entries above are Black's own responses to 1.Nf3/1.d4-style openings, not White repertoires with similar names — Opening Coach labels each one clearly by color when you pick it.
Weighted coach play
The coach picks between its important tries with realistic frequency, not a fixed script — so you see the lines you'll actually face.
Mistake-specific coaching
Common wrong replies get their own explanation wherever the catalog has authored one, not just a generic "not the book move."
Piece first, then destination
A first click shows which piece to move; a second reveals where — a real chance to work it out before the answer appears.
Target one line directly
Jump straight into a specific named variation from the setup screen instead of leaving it to the coach's random weighting.
Engine territory
Past the book, Stockfish plays both sides at full search depth — the board's own color change makes the shift impossible to miss.
Opening Stats feeds the plan
Your worst-performing opening by color is one click away from becoming your next Opening Coach session.
Explore the rest of the app
Opening Coach & Stats
You're here.
Import & Game Review
Unlimited Stockfish analysis and coaching notes on where your rating leaks.
Puzzles & Spaced Repetition
Puzzles built from your own blunders, plus single-attempt exams and short survival drills.
Bots & Opening Traps
An adjustable engine opponent and twenty scripted trap-heavy openings.