Every number on this site comes from Stockfish or Lichess — never invented.
Who built it
Chessy is a solo-built product. Every lesson is written and verified by code — not generated wholesale by an LLM — and grounded in Stockfish evaluations and Lichess statistics from hundreds of millions of real games.
How it finds your leak
Chessy pulls your real games from Chess.com or Lichess and runs every move through Stockfish, the world's strongest open-source engine, at depth 12–16. It groups your mistakes by pattern — hanging pieces, missed forks, opening traps — and surfaces the single one costing you the most rating. That's your leak.
From there you drill puzzles built from your own blunders until the pattern stops recurring. Chessy tracks the leak's frequency over time and marks it FIXED when it genuinely disappears from your games — not after a fixed number of reps, but when the evidence says so.
Data sources
Stockfish — every position evaluation (centipawn score and best continuation) on Chessy is computed directly by Stockfish, not estimated or copied from another source.
Lichess — the largest open chess database. Win rates, game counts and top continuations come from Lichess's opening explorer API, covering hundreds of millions of rated games across all time controls.
Clara — a chess-playing model trained to imitate how humans at a given rating actually play, used on the "Analyze with Clara" tab to show what a player at your level would typically do in a position — not just what the strongest engine move is.
The free interactive lessons
Separately from the leak-fixing product, every opening lesson on Chessy includes a free drill: you play the line against a real Stockfish opponent that adapts its strength to your level. No downloads, no signup, no cost.
Signing up (also free) unlocks the leak-fixing loop above, plus move-by-move AI coaching and a personal Telegram coach that reviews your real games.
Why the content is trustworthy
Each fact on a lesson page — win rate, game count, Stockfish evaluation, ECO code — is pulled from the source at page-generation time and embedded directly. There is no editorial padding or invented claims; if a number appears, it comes from Lichess or Stockfish.
AI coaching text is grounded: the coach sees the engine's actual verdict on each move before commenting, which prevents the invented threat lines and ownership confusion common in other AI chess tools.