Compatibility Plugin
Since this version of Joomla has not been released yet, this page can change anytime.
Heads-up, don't create a plugin as behaviour plugin because it's possible that this group get removed at some point.
Joomla 5 Compatibility Plugin
As part of Joomla! 5.0 a plugin was introduced which enhance backward compatibility between Joomla 5 and 4. Please check the Backward Compatibility Plugin for more details.
For more detail check Compatibility Plugin Joomla! 5.0.
Joomla 6 Compatibility Plugin
In Joomla! 6.0 the Compatibility Plugin introduced in Joomla! 5.0 will be replaced by a new plugin called "Behaviour - Backward Compatibility 6".
Despite the warning about the potential removal of the behaviour plugin type, this compatibility plugin still uses
this type to ensure it loads before any other plugin, as this is critical for backward compatibility functionality.
Detailed documentation
Please read the Compatibility Plugin 6.0 section