OPENINGPREP

Enter a Lichess or Chess.com username and a color. We read that player's most recent public games and show the lines they play most, how they score from each, and where their own moves leave the opening encyclopedia.

Enter your email to use this tool

Opening Prep is free. Enter your email and the tool opens right away. No account and no password.

Where the data comes from

Games: the public game archives of Lichess and Chess.com, read through their public APIs when you ask. No sign-in, no private data. Variants and games from a set-up position are left out, and closed accounts are not read.

Theory: the open lichess-org chess-openings list (CC0), matched by move order, and the masters statistics ASCENDCHESS keeps.

A report is not saved and is not listed by search engines. The games read are kept for up to 6 hours, so a repeat lookup does not ask the site again.

Questions

What is an opening tree?

It is every line a player chose in their games, merged move by move, with how often they played each move and how they scored after it.

What counts as theory here?

A move is in the encyclopedia when it follows a line in the open lichess-org chess-openings list. Leaving it is not a mistake; it only marks where the player is on their own.

Why can the same position appear twice?

Lines are grouped by move order, so two move orders that reach the same position stay separate.