ORBT Chess

Opening Repertoire Builder & Trainer · said “orbit”

Build an opening repertoire you actually know.

See every opponent move you haven't prepared, choose your answers with the explorer and the engine, and learn them with spaced repetition. Free and open source, for iPhone, iPad and Mac.

Download on the App Store Source on GitHub
ORBT Chess on iPad: the repertoire list beside the Najdorf, with White's replies and how often each is played ORBT Chess on iPhone: studying the Najdorf, asked to play d6

How it works

Build it, check it, learn it.

  1. 1

    Build

    Pick your moves with the numbers

    Every move shows how often it's played, how it scores and the engine's evaluation. Choose the moves that work, follow the coverage to the next reply that needs an answer, or enter lines you already know.

  2. 2

    Analyse

    Find out why a move fails

    One tap opens the position on an analysis board, with the moves that led there. It shows Lichess's stored engine evaluation when there is one, and otherwise runs Stockfish on your device.

    AnalysisCloud · depth 54
    +0.36. h3 e6 7. g4 d5 8. exd5 Nxd5
    +0.26. Be3 Ng4 7. Bc1 Nf6 8. h3 e6
    +0.26. f3 e5 7. Nb3 Be6 8. Be3 Nbd7
  3. 3

    Find the gaps

    See what you haven't covered

    Set a target such as “every move played once in 500 games”. ORBT lists each opponent move above it that you have no answer for, and how complete each line is.

  4. 4

    Study

    Learn it with spaced repetition

    Each position where it's your move is a flashcard, scheduled by Anki's algorithm and shown again just before you'd forget it. Study everything, or one branch. It all works offline.

    StudyNajdorf
    1.e4 c5 2.Nf3
    ✦New move: play d61910

Features

What else is in the app

Progress

Building and learning, apart

Coverage shows how complete your preparation is; the study counts show how well you know it.

Coverage databases

Statistics from players at your level

Pick a time control and rating range. Its statistics download once, then coverage works instantly and offline.

iPad & Mac

Room for everything

Your repertoires, the moves, the explorer, the engine and the board on one screen.

The analysis board on iPad with the repertoire list, the opening explorer, the move list and engine lines

Your files

Just a PGN

Each repertoire is a PGN file in your iCloud Drive, saved on every edit and synced to your other devices.

Works offline

No signal, no problem

Only fetching new statistics needs the internet.

✓Studying and drilling
✓Stockfish analysis
✓Coverage from the downloaded tables
✓Editing your repertoire

What's next

Android, Windows, Linux or the web?

Not built yet. ORBT's chess logic is a Rust core that could run on all of them, so the next platform depends on what people ask for.

  • iPhone, iPad and MacAvailable
  • AndroidNot built yet
  • Windows and LinuxNot built yet
  • WebNot built yet
Tell us which one you'd use

Open source

Free, and the code is public

No subscription, no ads, no tracking. ORBT is licensed under the AGPL-3.0: read the code, build it yourself, report an issue or send a pull request.

A Rust core

The chess, coverage and training rules are one Rust library with tests, shared by every platform. The app on top is SwiftUI.

Built on proven work

Anki's scheduler, ported from its source; Stockfish 19 on the device; statistics from the Lichess opening explorer.

Your data, your files

Repertoires are plain PGN files and training history is JSON beside them. No account needed.

Source on GitHub Build it yourself Report an issue

Built on Anki, Lichess, Stockfish, shakmaty and Lumbra's Gigabase. Pieces: cburnett (GPLv2+).