Play the engine
Sit down for a game at a strength that suits you. The engine plays real, principled chess — no canned openings or random blunders.
A chess coach that runs on your computer.
Play against the engine, get plain-language reviews of where your games went wrong, and train on puzzles built from your own mistakes. No account, no subscription, no internet required.
Free & open source · Windows, macOS & Linux
Built to help you actually improve
Understand your mistakes
After a game, Focalors explains why a move was bad in words: a hanging piece, a worsening pawn structure, lost king safety — not just a number.
Train on your weaknesses
Puzzles are drawn from positions you misplayed, so you practise the exact patterns that are costing you games.
Your data stays yours
Every game, stat, and puzzle lives in a small file on your machine. No cloud, no tracking, nothing leaves your computer.
See the whole story of a game
The review screen pairs the board with an evaluation graph and a breakdown of how each phase went. Spot the moment a game turned, jump straight to it, and see the reasoning behind the swing.
Download Focalors
Free forever. Pick your system — your download will start a fresh, self-contained app. First-launch tips below.
Always the latest version, straight from GitHub Releases. Prefer to build it yourself? The source is on GitHub.
Questions
Is it really free?
Yes — completely free and open source under the GPL-3.0 license. There's no paid tier, no account, and no ads. You can read every line of the code on GitHub.
Do I need an account or an internet connection?
Neither. Focalors runs entirely on your computer. After you download it once, it works fully offline, and it never sends your games or data anywhere.
Is it safe to download?
The app is open source, contains no ads or tracking, and the downloads come straight from GitHub's official release page. Because it's made by an independent developer rather than a big company, your operating system may show a generic warning the first time you open it (see the next two questions) — that's standard for indie software, not a sign anything is wrong.
Windows says “Windows protected your PC” — what do I do?
That's Windows SmartScreen, and it appears for any app that hasn't paid for an expensive code-signing certificate. To continue: click More info, then Run anyway. You only need to do this once.
macOS won't let me open it — what do I do?
Right now the Mac build is a command-line binary for Apple Silicon (M1–M4) Macs, and macOS Gatekeeper blocks unsigned apps by default. After unzipping, you'll need to allow it via Terminal:
cd ~/Downloads/focalors-macos-aarch64
xattr -d com.apple.quarantine focalors
chmod +x focalors
./focalorsA friendlier Mac installer is on the to-do list. Intel Macs aren't supported yet.
What do I need to run it?
A 64-bit computer. Windows and Linux builds target any Intel/AMD chip from 2013 onward (AVX2). Mac requires Apple Silicon. The whole app is only a few megabytes and is light on resources.
How strong is the engine?
Roughly 2200–2400 Elo — strong enough to challenge and teach club players and well beyond. But the goal isn't to be the world's strongest engine; it's to help you understand your games. For raw strength, Stockfish exists; Focalors is about learning.
Who makes Focalors?
It's an independent project, built in Rust by a developer who loves chess and wanted offline learning tools that respect your data. Full credits are on GitHub.