Endgame books cover every ending in order. Your games only reach some of them. The Endgame Trainer reads up to 500 of your games from Chess.com or Lichess, sorts every endgame position you played by its material, and measures your accuracy in each type. Practice starts with the ending where you score lowest.
Endings are grouped the way players think about them: pawn endings, rook endings, bishop and knight endings, queen endings, the combined ones such as rook and bishop, and mixed endings. For each type you reached, you see your accuracy and how many games it came up in.
Accuracy is measured move by move with Stockfish 18 running in your browser, the same way a Game Report grades a game.
Start Training serves endgame puzzles of that type, taken from real games and matched to your rating. Endgame puzzles tend to run longer than most tactics, because the point is technique: carrying an advantage over several moves rather than finding one shot.
If none of your games reached an ending worth training on, the trainer works through the endings every player needs, starting with pawn and rook endings.
Bring your king into the game as soon as the queens are off: in the endgame it is a strong piece, not one to hide. Put rooks behind passed pawns, your own or your opponent's. Before a pawn race, count the moves for both sides rather than guessing. And before trading into a pawn ending, check that the pawn ending is actually won, because it cannot be undone.
These are simple to state and easy to forget with the clock running, which is why practising them in real positions works better than reading about them.
Games that reach an ending are often decided by technique rather than tactics: counting tempi in a pawn race, cutting off the king in a rook ending, knowing when to trade into a won pawn ending. These skills repeat from game to game, so time spent on them keeps paying back.
Endgames are where many winning positions are thrown away, and Advantage Conversion trains finishing them against the computer. For the full picture of how you play each phase of the game, run a Profile Report.
Pawn, rook, bishop, knight and queen endings, combined endings such as rook and bishop, and mixed endings.
Real games: endgame positions that actually arose at the board, matched to your rating.
Then there is little to rank, and the trainer takes you through the endings every player needs, starting with pawn and rook endings.