Joomla! 3.8 is the ninth standard-term support release in the Joomla 3 series. It was released on 19 September, 2017. This release features over 300 improvements to the CMS, with two primary major features aimed at developers: the new routing system and the beginning of a forward compatibility layer with Joomla! 4.0. Additionally, two security issues have been resolved.

New and Improved Routing System

The new routing system gives users more control over their URL structure, including the ability to remove IDs from URLs. Designed to help you improve SEO, you can benefit from these improvements instantly.

Joomla! 4 Compatibility Layer

The development on Joomla! 4 has made some changes in how the core code is structured by migrating classes to use PHP namespaces. Joomla! 3.8 includes a mapping layer to allow developers to use the older class names while being able to take advantage of the new class name structure. 

To make extension development and transition smooth, the majority of the core library classes have already been namespaced in Joomla! 3.8 with class aliases in place to ensure backwards compatibility.

Improved Sample Data Installation

It is now possible to install sample data within your site back end after finishing the installation process. This can allow users to create their own generic data sets or extension developers to provide easy-to-install sample data for their extensions.

Sodium Encryption Support

PHP 7.2 introduces the new sodium extension for processing encrypted data, through a polyfill of this library. Joomla! makes this new API available for all of users even before they upgrade to PHP 7.2.

Additional Features and Improvements

Event hook for frontend mod_stats: The module can now be expanded with custom statistics from any source

Add a CSS class to menu item images: Provides more styling options to images set to menu items

Tags: Select category and tag while creating a Category Blog menu item and filter tags in your module Articles - Categories

Backend Menus: Your menu modules can be tagged and displayed per available administrator languages

Meta tag improvement: Ability to add multiple versions of the same <meta> tag

Archived articles Menu Type: You can now filter your archives by a given category.

Featured Articles: Schedule when to start and stop featuring an article

Backend Menu Customization: Create your own preset menu, transform your custom menu into a preset one and override the layout

New filtering option: Filter your menu items list by Parent Menu Items only

Redirect Plugin: A new modal window allows you to edit the plugin settings in one click

Session handler: Redis Session Support has been added to Joomla! 3.8