Know your opponent before the first move.
Free during Early Access. Choose public Chess.com or Lichess accounts, or upload a tournament PGN and select the participant you are preparing for. You can include several accounts; this privately groups sources without asserting that their identities are verified.
A report about the player
ChessSum studies the selected player’s games: their openings, recorded moves, results and repeated mistakes in the computer-checked sample. Reports do not use the reader’s own games. Choose the player’s color to inspect their White or Black games.
Explore the evidence, then practice
Open the supporting games, inspect conditional move frequencies and ask the chess engine to analyze a position. Historical popularity is distinct from engine quality. Practice checks legal moves and allows sound alternatives at the available analysis depth.
What can you search?
Online usernames and participants in your private PGN uploads. No external worldwide OTB database is connected. Names without a source player ID need your confirmation; similar names across databases are not automatically merged.
Coverage and uncertainty
Reports use available imported games within the selected filters and workload limits. Unknown dates or ratings remain unknown. Recent changes compare source and time-control pools separately. A low win rate does not establish an engine-confirmed weakness, and history cannot guarantee an opponent's next move.
Save privately, or share a player report
Analysis requires an account. Saved reports stay private until their owner creates a share link. Anyone with the link can browse that saved version without signing in; starting a new analysis still requires an account. Links can be disabled at any time. Sharing supports public online games; reports containing uploaded PGNs stay private. Personal settings and upcoming tournament details are excluded.
Prepare for an Opponent →