.htaccess webp redirection if exists and client accept header permits

.htaccess

<IfModule mod_rewrite.c>
  RewriteEngine On
  RewriteBase /
  # check if browser accepts webp
  RewriteCond %{HTTP_ACCEPT} image/webp

  # check if file is jpg or png
  RewriteCond %{REQUEST_FILENAME} (.*\.(jpe?g|png))$

  # check if corresponding webp file exists image.png -> image.webp
  RewriteCond %1\.webp -f

  # serve up webp instead
  RewriteRule (.+\.(jpe?g|png))$ $1.webp [T=image/webp,E=accept:1]

</IfModule>