• How to remove .php, .html, .htm extensions with .htaccess
• How to remove .html from URL?
• Remove .html and .php extensions with .htaccess
• How to remove .html extension from URL of a static page

To remove the .php extension from a PHP file

RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^([^\.]+)$ $1.php [NC,L]

To remove the .html extension from a PHP file

RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^([^\.]+)$ $1.html [NC,L]

To remove the .htm extension from a PHP file

RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^([^\.]+)$ $1.htm [NC,L]