ExpressionEngine® 3 User Guide

Legacy Documentation

You are using the documentation for version 3.5.17. Go here for the latest version or check here for your available upgrades to the latest version.


ExpressionEngine is the ultimate in flexibility, designed to be a platform for developers to easily extend to enable rich functionality. Like an operating system, it ships with a set of “apps” to cover the basic necessities right out of the box. We call those apps Add-Ons.

Have a need for RSS? Search? Comments? Install those packages, and you’ll have a whole new set of tools at your disposal.

And just like an OS, Add-Ons that don’t come included with ExpressionEngine can be added to bring even more functionality to the platform. ExpressionEngine was built on a CodeIgniter foundation and includes a robust developer API to enable rapid Add-on development, and a rich ecosystem filled with high-quality Add-Ons has grown up around it.

With Add-Ons available from EllisLab for download and third-party developers, you can construct a web publishing system tailored to fit the needs of the project at hand.