Joomla! 5.0 introduced the Backward Compatibility Plugin.
Joomla! 6.0 replaced the Backward Compatibility Plugin with the Backward Compatibility 6 Plugin.
In this article we shall refer to both simply as the Backward Compatibility Plugin.
The Backward Compatibility Plugin is enabled by default in the Joomla! CMS.
Purpose: to enable Third Party Extensions which are not compatible with Joomla! 5+ to function after you update your website's Joomla! CMS from an earlier version.
Backward Compatibility Plugins in Joomla! 5.4+
The Backward Compatibility introduced by Joomla! 5.0 was added to by the Joomla! 5.4 update process in readiness for Joomla! 6+
Backward Compatibility Plugins in Joomla! 6.0+
The old Backward Compatibilty Plugin was removed by the Joomla! 6.0 update process.
Fresh installations of Joomla! 6+ include only one Backward Compatibility Plugin - see image.
Should you disable the plugin?
If your Joomla! 5+ website is using an extension which you know the developer has no plans to make it compatible with Joomla! 5+ then you may wish to find an alternative extension to use.
Reason: use of the Backward Compatibility Plugin is reported to have a marginal adverse impact on performance.
Page load times may be marginally slower.
If all your website's Third Party Extensions are compatible with Joomla! 5+ then you may wish to disable the Backward Compatibility Plugin. Doing so may marginally improve page load times.
Caution: it is advisable to disable the Backward Compatibility Plugin in a test environment before doing so on a live website.
Useful Links
The Joomla! Project has published a useful guide at the following link.
Read More: Issues to consider before you disable the Backward Compatibility Plugin
The Joomla! Community Magazine February 2024 edition included the following interesting article.
Read more: The Backward Compatibility Plugin and why you should switch it off
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