Rewrite rule which strips all query params where the key begins with "utm_" (Google Analytics)

  # Google Analytics & Campaign Monitor
  # Removes all query params where the key begins with "utm_"

  # Skip the rewrites if no "utm_*" key exist.
  RewriteCond %{QUERY_STRING} !(^|&)utm_ [NC]
  RewriteRule .* - [S=3]
  
  # Check and handle first query param.
  RewriteCond %{QUERY_STRING} ^utm_[A-Za-z0-9]+=[^&]+(.*) [NC]
  RewriteRule (.*) /$1?%1 [R=301,L]
  
  # Check and handle every other query param.
  RewriteCond %{QUERY_STRING} (.*)([?|&]utm_[A-Za-z0-9]+=[^&]+)(.*) [NC]
  RewriteRule (.*) /$1?%1%3 [R=301,L]
  
  # Minor cleanup. Removes an ampersand if it is the first character in the query string.
  RewriteCond %{QUERY_STRING} ^&(.*) [NC]
  RewriteRule (.*) /$1?%1 [R=301,L]