Tools - Settings - View - Viewer -
Under "Tools → Settings → View → Viewer" in the tab "Plugins" the following settings are offered for the viewer and/or the quick viewer.
These settings are applied for the:
The following buttons are available for editing the list of viewer plugins:
In the input box "Detect string", enter the file extensions which will be viewed by the highlighted plugin.
In the input box "File name", the path and filename of the plugin can be specified in the same way as with the button.
If this setting is checked, FreeCommander first analyzes whether a plugin can open files with a given extension. The listed plugins are analyzed sequentially from the top down. The highlighted file is opened by the first plugin with a matching extension in the detect string. Only checked rows are taken into account.
If a plugin has no file extension assigned in its detect string, FreeCommander then analyzes whether this plugin can open the file natively.
If no plugin fits, then FreeCommander tries to open the file with an internal viewer.
If this setting is not checked, FreeCommander analyzes whether the file can be opened by an internal viewer listed in the viewer tab "General".
In this case plugins can be activated only with the menu item "View → Plugins" in the viewer window.