RewriteEngine On

# Remove .html extension from URL
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME}.html -f
RewriteRule ^([^\.]+)/?$ $1.html [NC,L]

# Set index.html as the default document
DirectoryIndex index.html

# Redirect .html URLs to non-.html URLs
RewriteCond %{THE_REQUEST} \.html
RewriteRule ^(.+)\.html$ /$1 [R=301,L]