Extensions extend the functionality of Joomla. A Joomla 3 installation comes with many core extensions included, but there are hundred more to choose from at extensions.joomla.org. You can now choose to Install from Web in the Extension Manager similar to the way Wordpress allows to to install plugins.

There are five basic varieties of Extensions for Joomla:

Components: like little mini-applications that perform specific tasks.

Plug-ins: provide functions for trigger events or things like the text editor, buttons, authentification, etc..  Plug-ins are often installed in conjunction with Components.

Modules: this are used to render the web page. They are the boxes in which you can place menus, advertisements, login forms, etc.  Module Manage creates and places these modules in the page and position specified.

Templates: These Extensions control the look and feel of your site.  They each have a framework of positions for you Modules and a stylesheet(s) to modify the look of your site.

Languages: You can install Language Extensions to provide languages other than English.

The built in Joomla Extensions are listed under Manage in the Extension Manager. You can tell the core Joomla Extensions in the list because their Author is Joomla! Project.  Some of these will have lock symbols under status.  This means that Joomla requires that these extensions are loaded an enabled in order to run properly.

Things to consider when installing 3rd Party Extensions

3rd Party Extensions can greatly expand the functionality of your site, but you do want to be careful in the selection of the extension and in the installation. Here are some questions to ask before installing extensions:

  • Will this extension work with my Joomla version?
  • Is this a reliable provider, will they provide support, will they be there 3 years from now?
  • What happens with this extension if I upgrade my Joomla to a newer version?
  • How popular is this extension? The more popular, the more likely it is one that works well.
  • If it is a paid extension, is there a free one that will do the same thing? Is it worth the cost? Does support come with the initial price?
  • Will this extension crash my site due to conflict with other installed extensions?
  • Will this extension open up security risks?
  • Will the extension slow down my site?

The best method for installing extensions is to choose reliable providers, popular extensions, minimize the number of extensions and always check the Joomla Vulnerable Extensions list. ALWAYS backup up your site files and database before installing any extension.