About Repertoire Builder

What this is

Repertoire Builder shows chess opening win rates, common replies, and rating-band repertoire trees, all computed directly from real games via Lichess’s public API and Opening Explorer. Nothing here is opinion or an engine evaluation dressed up as statistics — every percentage, table, and “common mistake” callout on this site traces back to an actual count of games played at that rating.

Why it exists

Most opening guides describe a line in the abstract, without saying how it actually performs for players at your own rating. This site pairs each opening with the data: how it scores at 1400-1600 versus 2000+, what opponents actually play in reply (not just the “book” line), and where real games at your rating band tend to go wrong.

How it’s built

Every page is generated from Lichess’s public, keyless Opening Explorer API and the general Lichess API — no proprietary or private data source is used. Pages are pre-rendered as plain static HTML; the player-lookup page is the one exception, calling Lichess’s API directly from your browser so it can look up any username on demand.

Who runs this

This site is independently run. No individually-attributed author byline is published on these pages at this time — where authorship needs to be named (for example, in structured data on article pages), it is attributed to Repertoire Builder as a publisher rather than to an invented person.

Support

This site is free to use. If you find it useful, voluntary support links appear in the footer of every page (Ko-fi, Buy Me a Coffee) — see the disclosure note there for what that does and doesn’t mean.

Questions

See the Contact page.