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Satranç Online

Strong engines. Clear explanations. No installation.

What is Satranç Online?

Satranç Online is a free, browser-based chess platform for playing against multiple chess engines and reviewing games with understandable analysis. It combines UCI chess engines, a touch-friendly Chessground board, move-by-move evaluation and concise AI explanations in one interface.

It was created because using strong engines often means installing desktop GUIs, finding compatible binaries, configuring UCI options and interpreting raw engine output. Satranç Online removes that setup. Open the site, choose an available engine and play.

Play nowView source on GitHub

Why it exists

Access

Make strong chess engines usable without downloads, engine folders or desktop configuration.

Understanding

Turn raw evaluations into percentages, classifications, graphs and short explanations.

Choice

Let players compare engines with different search and evaluation approaches.

Open development

Build transparently on public, open-source chess technology.

Supported chess engines

The application registry supports the engines below. The live engine selector only shows engines whose executable is present and healthy on the deployed server.

Stockfish

Primary analysis engine and one of the strongest open-source chess engines. Excellent tactical search and general analysis.

Official siteGitHub

LCZero / Leela Chess Zero

Neural-network engine inspired by AlphaZero, known for positional and long-term evaluations.

Official siteGitHub

Koivisto

Strong open-source UCI engine with modern search and evaluation, compiled in a portable server build.

GitHub

PlentyChess

Strong NNUE-based UCI engine using efficiently updated neural evaluation.

GitHub

Reckless

Compact UCI engine configured for efficient server use and practical play.

GitHub

Berserk

High-performance open-source NNUE engine with strong practical play.

GitHub

Ethereal

A strong GPLv3 UCI engine using alpha-beta search and neural evaluation.

GitHub

Crystal

Stockfish-derived engine designed to expose tactical and positional weaknesses more clearly.

GitHub

Patricia

Aggressive open-source engine tuned for attacking and entertaining chess.

GitHub

Viridithas

Modern open-source UCI engine developed for strong tournament performance.

GitHub

RofChade

Competitive UCI chess engine with classical search and NNUE-era development.

Project reference

Fruit

Historically important open-source engine that influenced many later chess-engine designs.

ChessProgramming

Cheng4

Lightweight UCI engine used as an additional practical opponent.

ChessProgramming

Maia 1100 / 1500 / 1900

Human-like LC0 networks trained to predict moves at different rating levels. Satranç Online runs them with a one-node search.

Official siteGitHub

Satranç Online Engine

An in-process experimental engine included in the project for custom gameplay and development.

Source

Features

Multi-engine play

Choose any currently available server engine.

Difficulty and depth controls

Use presets or set engine search depth manually.

Touch-friendly board

Chessground supports drag-and-drop and tap-to-move on desktop, tablet and mobile.

Board and piece themes

Brown, blue and green boards with Merida, Cburnett and Alpha pieces.

Position advantage

White/Black advantage percentages derived from engine evaluation.

Per-move analysis

Every ply records the played move, best move, evaluation change and win-probability loss.

Move classifications

Best, Excellent, Good, Inaccuracy, Mistake and Blunder labels with mate-aware rules.

Evaluation graph

Visualize how the position changed throughout the game.

Opening recognition

Match early moves against a local ECO-style opening database.

Explain this move

Click a classification badge to ask why the move was weak and what the engine preferred.

AI Coach

Groq produces concise commentary for important moments; OpenAI is the fallback.

Smart silence

The coach avoids unnecessary model calls on ordinary moves.

Undo and New Game

Accessible controls with confirmation before discarding a game in progress.

Responsive and accessible UI

Visible keyboard focus, disabled states, reduced-motion support and careful live regions.

PWA support

Installable from supported browsers with local first-party assets.

No registration required

Start playing immediately. Login and saved history are not required for core play.

How analysis works

  1. Stockfish evaluates the position before and after each move.
  2. The server checks whether the played UCI move equals the engine best move.
  3. Centipawn evaluations are converted into approximate position probabilities.
  4. Mate threats are handled separately from ordinary numerical evaluations.
  5. Results are cached by position, move and depth to reduce repeated engine work.
  6. Groq or OpenAI explains the verified engine data; the language model does not decide the chess score.

Technology and open-source credits

  • Node.js
  • Express
  • Chessground
  • chess.js
  • UCI
  • Stockfish
  • LCZero
  • Groq
  • OpenAI fallback
  • Docker
  • Render
  • GitHub Actions

Satranç Online depends on the work of chess-engine authors and open-source maintainers. Engine names and trademarks belong to their respective projects and owners. Chessground is GPL-3.0 licensed; the Satranç Online source repository is public.

Privacy and operating model

Core play does not require an account. Engine computation runs on the server. AI explanation requests send the PGN and verified engine evidence to the configured provider. API keys are kept on the server and are never exposed to the browser.

Roadmap

  • Accuracy scores for White and Black
  • Saved games and optional player accounts
  • PGN import and export
  • Opening explorer
  • Advanced engine configuration
  • Engine comparison and tournaments
  • Developer API after usage and demand justify it