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Compatibility Plugins

Joomla 6 Compatibility Plugin​

The ‘Behaviour – Backward Compatibility 6’ plugin is essential for the migration from Joomla! 5.4 to 6.x.

In Joomla 5.4, this plugin is installed and enabled by default, but it does not perform any actions. Its presence ensures that when the site is upgraded to Joomla 6, the updated code can run immediately, and any third-party extensions requiring the plugin to be enabled in Joomla 6 will not cause the update to fail.

As a behaviour-type plugin, it loads before any other plugin — a critical requirement for ensuring backward compatibility.

For upgrades from Joomla! 5.4 to Joomla! 6.x, it is mandatory that this plugin is both installed and enabled. To review which backward compatibility cases have been removed, see Removed and Backward Incompatibility.

NEW INSTALLATIONS

For new Joomla! 6.0 installations, the ‘Behaviour – Backward Compatibility 6’ plugin is installed but disabled by default.

Related PRs are:

  • 45336 Introduce Joomla 6.0 compatibility plugin
  • 45371 Add compat6 behaviour plugin to 5.4 so it is available and enabled when updating to 6.x.
  • 45480 Introduce Joomla 6.0 compatibility plugin
  • 45493 Add pre-update checks for backward compatibility plugins for update to Joomla 6
  • 45525 Add compat6 behaviour plugin to 5.4 with enabled options
  • 45973 Don't insert duplicate records in update SQL scripts when they are executed multiple times
DEVELOPER NOTE

Avoid creating your own plugin within the Behaviour group, as this group may be removed in a future release.

Joomla 5 Compatibility Plugin​

Introduced in Joomla! 5.0, the ‘Behaviour – Backward Compatibility’ plugin improves compatibility between Joomla 5 and 4.

When upgrading from Joomla! 5.4 to Joomla! 6.x, this plugin must be disabled before starting the upgrade. If the site fails to load after disabling it in Joomla 5.4, simply re-enable the plugin to restore functionality. The errors should then be investigated and resolved while still running Joomla 5.4, before attempting the upgrade again.

This approach ensures that any incompatibilities are detected and fixed safely in the Joomla 5.4 environment, avoiding partial or corrupted upgrades that may occur if the site crashes during the upgrade process.