The engine analysis is a complex feature, requiring several aspects of your system to work correctly for the feature to behave as intended. If any of these aspects are not working, the analysis may not work, or may work poorly.

The engine analysis feature uses a Java Applet to communicate with the engine running on your machine, and requires the latest version of Java to be installed. Older version of Java will probably not work. The official Sun/Oracle version of Java is also required. Systems such as Linux which rely on OpenJava and the Iced Tea Java plugin will need to install the official Sun/Oracle version of Java and the Java plugin. You will also need to give permission for the Java applet to run the engine on your local machine, this permission should be requested the first you access the engine analysis feature (usually via the engine settings page).

It is important that your engine supports the UCI protocol. The latest version of commercial engines such as Rybka and Shredder all support the UCI interface, Fritz and the chess master interface (also called 'The King') do not. Most freely available engines (such as Stockfish) also support UCI, one notable exception is "Crafty", which does not. To test if your engine supports UCI, run the engine from the command line and type "uci" (without the quotes) and press return. If your engine is UCI compatible it should output a list of options, finishing with "uciok".

Some web browsers do not support the interface required to communicate between the browser and the Java applet which talks to the engine. The latest versions of Firefox, Google Chrome, Safari and Internet Explorer all work. Unfortunately Opera does not appear to work at the moment. Google Chrome is currently the best browser to use with this feature as it is the most efficient in terms of updating the display. Firefox 4.0 when it becomes available should also be able to provide equivalent performance. Internet Explorer versions 8 and below are not recommended due to their poor performance characteristics.

The analysis feature attempts to avoid loading the Java applet until analysis is actually requested. This avoids having to load the Java plugin unless it is required (a process that takes several seconds if it is not already loaded). Unfortunately not all operating systems support this deferred loading, at least some versions of Windows Vista do not work with deferred loading. If you are having trouble getting the engine to load when required, you may need to turn off the deferred loading. You can do this by going to the "Chess Engines" tab on your preference settings and turning on the 'Initialise Engine When Page Loads' setting.

Chess engines use a large amount of your available CPU, and this may result in your web browser becoming slow while the engine is running. If you are using a multi core or multi CPU machine, you may find the browser works better if you limit the number of CPUs the engine is allowed to use. This can usually be done on the engine settings page, but different engines have different names for this setting, "Threads" and "Max Threads" are two examples, but other engines may use "Max CPU" etc. The manual that comes with your engine should explain the appropriate setting. If you browser is slow while using analysis, you may also consider using Google Chrome for your browser given that is currently the best performing browser.

If you continue to have problems getting the engine analysis to work, please try to change your Java settings so that the Java console is displayed, and post a bug report in the forum with any output you find in the Java console.