Redirect all requests to default documents to their parent directory instead. This is an important SEO tactic to avoid duplicate content penalties due to both /directoryname/ and /directoryname/index.php both returning the same document response. This redirect should be Permanent (301).
Refer also to: Virtual Host Config or .htaccess?
To redirect all requests to one or more default documents to the parent directory url, add the following rule:
RewriteRule ^/(.*)index\.(php|html) $1 [R=301,L]
This rule would cause all requests to index.php or index.html anywhere in the site’s URL hierarchy to be redirected to the parent directory’s URL. For example, a request to /articles/index.php would be redirected to /articles/.
Change the file extension list (php|html) to your own website/language’s default document(s). Separate multiple entries with the pipe | symbol.