I am experiencing duplicate URLs like -2, -3, etc. What should I do?

If you are facing duplicate content items links e.g. http://yoursite.you/article.html, http://yoursite.you/article-2.html, etc. that lead to the same content, this is most probably caused by so called "Itemid" variable (although there may be other reasons also).

The Itemid is internal Joomla! variable used to identify the source of a URL link. E.g. main menu or sub menu item that your visitor used to get to a certain content. According to this variable, different Joomla! configurations are applied - e.g. what template will be used or what modules will be visible, etc.

Since JoomSEF 1.4.0, several new configuration options are provided in "Advanced configuration" section. The option "Exclude source info" may be used to exclude the Itemid variable from the URL and thus eliminate the duplicates caused by it. However, ignoring it completely may lead to unwanted Joomla! functionality, like not swithing the templates as desired or so. Whether this will be a problem for you or not depends mainly on the way how your site is designed and how complicated it is. If you need to fix this, the Itemid should be "reappended" to the SEF URL as an extra part using the option "Reappend source". Then the resulting URL will look like http://yoursite.you/article.html&Itemid=xy.

Since JoomSEF 2.0.0 there is a possibility to set your own Itemid for each extension that will always be used with it - thus even when "Reappend source" is set to Yes, that extension won't have the ?Itemid=xy appended. You can find this option in extension parameters. If you leave the "Override Itemid" field blank, the default Itemid will be used, but won't be appended as ?Itemid=xy in URL. Thus you can achieve that the ?Itemid=xy will be added only to those extensions that need it (mostly content). But be careful, setting Itemid to some random number can ruin your menu functionality!

Another new option is "Ignore multiple sources". If selected, only one URL will be created for each page using the first Itemid. Every other link varying in Itemid only will be ignored and the already created one will be used instead. But again - this can ruin your menu functionality! This option has no effect on extensions with custom Itemid set.