Play your opening against Stockfish. Then find out if you actually understood it.
Play your repertoire line from memory. Miss a move and you get the lesson's own reason the moment it happens. And once per run, Stockfish leaves the script with a good move you never rehearsed — so you find out whether you know the position, or just the sequence.
- Your line
- Off book
- Play it out
- Results
Stockfish left the book with 4.d3 — find a good reply.
How a run works
Pick an opening
Any opening in your repertoire, as White or Black — open its card and tap Practice.
Play your line
Stockfish plays the other side. A wrong move is re-asked, not skipped, with the lesson's why. Two misses on a move earn a text hint, three an arrow.
Go off book, play it out
Once per run Stockfish deviates. When the book ends, you play up to eight more moves, each graded, and the run hands you two scores.
Book move
4.c3
Stockfish played
4.d3
- Never in Stockfish's first two moves
- Costs at most 0.6 pawns against its best move
4…Nf6 is your book move, but the position has changed.
A line is a script. Once per run, Stockfish won't follow it.
A script is memorisable without understanding a move of it. So once in a run, Stockfish quietly refuses to play its half: it plays a different move that is still good. Two fairness rules apply — never in its first two moves, and never a move that gives up more than 0.6 pawns against its best, checked at depth 12 across four candidate lines. Play your memorised answer anyway and the run tells you: that's your book move, but the position has changed. And if no candidate survives the filter, the scripted move plays and the results say Stockfish stayed in the book.
5…Nxd5? walks into 6.Nxf7 — the Fried Liver. 5…Na5 hits the bishop and keeps your knight out of it.
- Miss 1 · re-asked
- Miss 2 · text hint
- Miss 3 · arrow on the board
Explained with the lesson's own reasoning, not a buzzer
Every miss goes through the same wrong-move coach every lesson uses: the lesson's authored explanation of why the tempting move fails, or the engine's own facts when there is none. The move is re-asked, not skipped. Miss it twice and you get a text hint; three times, an arrow on the board. You leave the run knowing why each move is the move — which is the part that survives when an opponent varies on move nine.
Line accuracy
92%
Play-out score
71
Form 84 · last 5 runs
Trending up over your last 3 runs
Play it out, then see your Form
When the book runs out — yours or Stockfish's — you play up to eight more moves of real chess. Each one is judged Best, Excellent, Good, Inaccuracy, Mistake or Blunder by the same classifier the game report uses, and averaged into a play-out score from 0 to 100. Line accuracy and play-out score come back separately, on purpose: knowing the moves and being able to play the position are different skills. Every opening card then shows a Form score from your last five runs — 70% line, 30% play-out — banded strong, steady or shaky, with a trend once you have three runs behind you.
What a run gives you
110 openings, White or Black
Every opening lesson you've added to your repertoire can be run, from either side of the board.
One deviation per run
Never in Stockfish's first two moves, never a bad move — and if nothing qualifies, the book plays through.
Eight graded moves
Real chess after the book ends, each move classified like a game report and averaged into one score.
Form from your last five runs
Strong, steady or shaky, with a trend from your third run. A run never touches mastery or your 90-day review — Verify does that.
Know the line. Play the position.
Building your repertoire is free on every plan. Practising a line against Stockfish is a Knight+ drill: preview the first three moves of any run, and finish one full run free before you decide.
Practice an opening