Hi,
Thanks for your question.
The system-j3.min.css and system-j4.min.css files are intentionally kept in Helix Ultimate for backward compatibility. These are legacy fallback styles and do not affect performance on Joomla 5 or 6.
Helix Ultimate does not currently use separate system-j5 or system-j6 CSS files. Instead, newer Joomla versions are handled through a more unified and optimized styling approach within the framework.
So there’s no need to remove these files manually—they are harmless and kept to ensure compatibility across different environments.
Please let us know if you need any further clarification.
Best regards,