BitSquareChess

A Very fast chess server

bitsquarechess in use: the opening explorer showing millions of games, and a game against Stockfish

26.4 million elite games

one native binary format · 5.33 GB

Instant opening explorer

~9 ms lookups · nothing downloaded

ECO codes & opening names

3,074 lines, from the corpus itself

Filter as you like

blitz / rapid / classical / titled / ECO

Play Stockfish

ten levels, in your own browser

Live engine analysis

eval bar · depth 25 and 3 lines on Pro

Games saved natively

the same .bsq format, with move times

Installs as an app

light, dark & system themes

Download all 26.4M games

Pro · 5.33 GB, streamed & verified

What you get

A chess database and engine that answer instantly, because the games are stored as raw bitboards and two-byte moves rather than text.

Live games with other players

Real-time matches with separate ratings for bullet, blitz, rapid and classical, and both clocks kept in sync by the server — so no drift, and no surprises when the flag falls.

Live tournaments

Scheduled arenas around the clock across every time control. Join the pool, get paired the moment an opponent is ready, and watch the standings move as results land.

26.4 million elite games

The full Lichess Elite corpus in a native binary format — 5.33 GB at 204 bytes per game, against roughly 14 GB for the same games in SQL. Every one of them verified to replay move for move.

Instant opening explorer

Roughly 9 ms per position, with nothing downloaded and nothing held in memory: each lookup pulls a few hundred bytes out of the index over a range request.

ECO codes and opening names

3,074 named lines derived from the corpus itself and keyed by position, so a transposition resolves to the same opening rather than falling out of book.

Filters that actually bite

Time control, titled players only, and ECO family — and they compose. Top-move average rating climbs from 2508 across all games to 2642 in classical games between titled players.

Play Stockfish, ten levels

From genuinely beginner-friendly to a serious fight. It runs in your own browser, so there is no queue and no shared server to wait for.

Live engine analysis

An evaluation strip under the board as you play, and your finished games saved on your device in the same binary format as the corpus, move times and all.

Free, or everything

Explore the whole database and play the engine without paying anything. Pro is for taking the corpus with you.

Free

£0 / forever

Everything you need to study openings and play.

  • Full opening explorer over all 26.4M games
  • ECO codes, opening names and every filter
  • Play Stockfish at all ten levels
  • Engine analysis to depth 12
  • Your games saved on your device

Pro

Pro
£4.99 / month

For keeping the database, not just querying it.

  • Everything in Free
  • Download all 26.4M games — 5.33 GB
  • Resumable, verified after download
  • Engine depth to 25, three lines
  • Cancel any time, handled by Stripe