The Backward Compatibility Plugin is enabled by default in the Joomla! 5 CMS.
Purpose: to enable Third Party Extensions which are not yet compatible with the Joomla! 5 CMS to continue to function after you update your website.
Should you disable the plugin?
If your Joomla! 5 website is using an extension which you know the developer has no plans to make compatible with Joomla! 5 then you should find an alternative extension to use.
If the developer indicates that their extension will be updated sooner rather than later, then you may wish instead to continue using the extension in the short term.
In the medium-long term you would however be well-advised to replace the extension or manage without.
Reason: whilst the Backward Compatibility Plugin is enabled it will adversely impact your website's performance.
Your website's page load times will be slower.
Disabling the plugin will improve page load speeds and also improve the prospects for a smooth upgrade to Joomla! 6 when it becomes available.
If all your website's Third Party Extensions are compatible with Joomla! 5 then you can safely disable the plugin.
Note: disabling the Backward Compatibility Plugin on a live production website runs the risk of breaking said website.
If in doubt, make a full backup and experiment with this plugin's settings offline.
The Joomla! Project has published a useful guide at the following link.
The Joomla! Community Magazine February 2024 edition included the following interesting article.
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