get_extensions_pattern(); $extensions = str_replace( '|avif', '', $extensions ); $home_root = wp_parse_url( home_url( '/' ) ); $home_root = $home_root['path']; return trim( ' # Vary: Accept for all the requests to jpeg, png, and gif. SetEnvIf Request_URI "\.(' . $extensions . ')$" REQUEST_image RewriteEngine On RewriteBase ' . $home_root . ' # Check if browser supports AVIF images. # Update the MIME type accordingly. RewriteCond %{HTTP_ACCEPT} image/avif # Check if AVIF replacement image exists. RewriteCond %{REQUEST_FILENAME}.avif -f # Serve AVIF image instead. RewriteRule (.+)\.(' . $extensions . ')$ $1.$2.avif [T=image/avif,NC] # Update the MIME type accordingly. Header append Vary Accept env=REQUEST_image ' ); } }