To enable Search Engine Friendly (SEF) URLs in Joomla!®, you must first enable RewriteBase in your .htaccess file.
.htaccess file. For more information, see Duplicate files or folders..htaccess_copy to .htaccess.bak. For more information, see Managing Your Hosting Account's Files..htaccess file.#:
You can now enable SEF URLs. If you need more help, see Enabling Joomla! Search Engine Friendly URLs.
If you encounter any issues, you can use .htaccess.bak as a backup of your .htaccess file.