Red Hot Pawn Chess is built on the work of a great many open source projects. This page records what we use, under which licence, and where to get it.
Chess Engine
Analysis, game review, puzzle explanations and the play-the-computer opponent are all powered by Stockfish, the open source chess engine, compiled to WebAssembly by the Stockfish.js project. It runs entirely in your own browser - positions are never sent to us for analysis.
Stockfish is free software licensed under the GNU General Public License version 3. We ship Stockfish.js 18 (lite, single-threaded) unmodified. Under the terms of that licence you are entitled to the corresponding source code, which is available from the project below.
Open Source Components
| Component | Used for | Licence |
|---|---|---|
| Bootstrap | Page layout and interface components | MIT |
| Bootstrap Icons | Interface and annotation icons | MIT |
| htmx | Loading page content without a reload | BSD 2-Clause |
| Vue | Live chess interface | MIT |
| Vue Toastification | On-screen notifications | MIT |
| Chart.js | Rating and evaluation graphs | MIT |
| chess.js | Move generation in the browser | BSD |
| Popper | Tooltip and dropdown positioning | MIT |
| mitt | Event handling in the board client | MIT |
| bootstrap-slider | Slider controls | MIT |
| jQuery | Older interface code | MIT |
| PHP | The language the site is built in | PHP License v3.01 |
| TypeScript | The language the chess board client is written in | Apache 2.0 |