Most ikiwiki plugins are perl modules and should be installed somewhere in the perl module search path. See the @INC list at the end of the output of perl -V for a list of the directories in that path. All plugins are in the IkiWiki::Plugin namespace, so they go in a IkiWiki/Plugin subdirectory inside the perl search path. For example, if your perl looks in /usr/local/lib/site_perl for modules, you can locally install ikiwiki plugins to /usr/local/lib/site_perl/IkiWiki/Plugin

You can use the libdirs and/or libdir configuration options to add directories to the search path. For example, if you set libdir to /home/you/.ikiwiki/, then ikiwiki will look for plugins in /home/you/.ikiwiki/IkiWiki/Plugin.

Ikiwiki also supports plugins that are external programs. These are typically written in some other language than perl. Ikiwiki searches for these in /usr/lib/ikiwiki/plugins by default. If libdirs or libdir are set, it will also look under those directories, for example in /home/you/.ikiwiki/plugins. Note that this type of plugin has to be executable for ikiwiki to use it.