GUI and Engine

Like all modern chess programs, Onno is designed for a software that consists of two parts. One part is the GUI, which you see on the screen and where you enter the moves. The other part is the engine, that evaluates the position and computes the computer’s moves. Engine and GUI communicate through the UCI protocol. In terms of non-computer chess, the GUI is the chessboard, the engine is the opponent.
Onno is only the engine, it does not have an own GUI. That means that you should download a GUI to play with Onno. If you don’t have a GUI yet, I recommend to get one of the following free GUIs:

  • Arena, if you basically want to play against the computer or let different engines play against each other. Arena is available only for Windows. Some people were successful in running it under Linux with Wine (but I wasn’t).
  • SCID, if you want to work seriously with chess databases. It is available for both Windows and Linux.

In addition, there are many other free and commercial GUIs that can be used together with Onno. Any UCI-compatible GUI should work.
Also, Onno makes intelligent use of the fuzziness of the UCI protocol definition to make the engine more usable from the command line without any GUI. But still this is recommended for geeks only.


  1. Download Onno
  2. Doubleclick on the file you have downloaded to unzip it. You can unzip to any directory you like, no further installation is required for the engine.
    • If you have administrator privilegesI suggest to unzip to C:\Program Files\OnnoChess or similar.
    • If you don’t have administrator privileges you can unzip somewhere below My Documents .
  3. If you don’t have a chess GUI yet, install one (see above).
  4. Wait for your license file to be emailed.
  5. Safe your license file to the same folder where you installed Onno.
  6. Install Onno in your chess GUI. Consult your GUI documentation for details.
    Here are instructions for Arena and SCID .
    If you have a 64 bit Windows version (Windows XP 64 or Vista 64) please install onno-1-0-x64.exe . Otherwise install onno-1-0-w32.exe .

Installation in Arena

Installation in Arena requires write permissions for the folder where Arena is installed. If you don’t have write permissions to that folder, your installation will disappear when you close and reopen Arena. You might also encounter other problems.
From the Engines menu, select Install New Engine . This browses for the engine; find Onno and press Open . This should prompt for the type, select UCI and press OK . Now you are asked “Start engine ‘Onno’?” Answer with Yes . In the analysis window, you should now read “Onno by Onno Garms”.
Optionally, you may enter some more information about Onno. To do so, from the Engines menu, select Manage . In the tab Details , select engine Onno .

  • Name might be changed to Onno 1.0
  • Author is Onno Garms
  • Country is Germany
  • A Logo file is provided in the distribution.

Installation in SCID

From the Tools menu, select Analysis Engine . Then press New . A new window should pop up. Enter the following information:

  • Onno 1.0 (or similar) for the Name .
  • Browse for the Command by pressing […].
  • Select UCI .
  • Other fields need no change.

Press OK .
It is highly recommended to check the installation as follows: In the Analysis Engine window, select Onno 1.0 and press OK . A new window should pop up which shows the analysis of the position that is currently on the board.
Note for Linux users: Be aware that symlinks are resolved at installation time.


Should you ever want to uninstall Onno, just uninstall Onno in your chess GUI and delete the folder where Onno is installed. Onno does not leave any footprints elsewhere.