Licences and credits
The open work Luftchess is built on, and the terms it comes under.
Updated 29 September 2026
Engines and data
| Component | Licence | How Luftchess uses it |
|---|---|---|
| Stockfish | GPL-3.0 | Runs on our server as a separate program. Luftchess sends it positions and reads its answers; its code is not part of Luftchess. Source: github.com/official-stockfish/Stockfish. |
| Leela Chess Zero (lc0) | GPL-3.0 | Runs on our server as a separate program: it plays the Maia networks, and on the Board it shows Leela's own natural moves and its feel for a position, with a network from lczero.org (T1-256x10). Its code is not part of Luftchess. Source: github.com/LeelaChessZero/lc0. |
| Maia | GPL-3.0 | Neural networks by the University of Toronto’s CSSLab that play like people; used for sparring. |
| Maia-3 | AGPL-3.0 | The newer human-like engine from the same lab, for the stronger sparring partners. It runs unmodified on our server as a separate program; its code is not part of Luftchess. Source: github.com/CSSLab/maia3. |
| Lichess tablebase | Lichess API | Exact results for positions with seven pieces or fewer, asked over the internet. |
| Lichess cloud evaluation | Lichess API | On the Analyse board, your browser asks it for stored engine lines of the position shown. Only the position is sent, with no names. |
| Lichess chess-openings | CC0-1.0 | The names of openings. |
| Lichess broadcasts | CC BY-SA 4.0 | The master games on the Board and in Games › Masters. They are stored as published; what Luftchess adds beside them is in the notice. You may reuse these games under the same licence. |
| Lichess and Chess.com public games | Their own terms | Public games, read through their public interfaces. |
In your browser
| Component | Licence | How Luftchess uses it |
|---|---|---|
| chessboard.js | MIT | The board in the app. |
| chess.js | BSD-2-Clause | The rules of chess in the app. |
| jQuery | MIT | Needed by chessboard.js. |
| marked | MIT | Shows formatted text in the app. |
| Chess pieces by Colin M.L. Burnett | BSD-3-Clause (text), one of the author’s options: GFDL, GPL, BSD and CC BY-SA 3.0 | The pieces in the app and on these pages. |
| Atkinson Hyperlegible Next, by the Braille Institute | SIL Open Font License 1.1 (text) | The typeface of these pages, served from our own server. |
On our server
| Component | Licence | How Luftchess uses it |
|---|---|---|
| python-chess | GPL-3.0 | Reads games and talks to the engines on our server. It is not sent to your browser. |
| Requests | Apache-2.0 | Fetches public games. |
| FSRS-4.5, by Open Spaced Repetition | MIT | Its formula and default weights decide when a practice position comes back. |
| Python and SQLite | PSF License; public domain | The server and its database. |
Thanks
Luftchess would not exist without the open chess world: the Stockfish and Leela teams, the Maia researchers, and Lichess, which publishes its games, its tablebase and its opening names for everyone. Luftchess is not affiliated with Chess.com or Lichess.