enabling apache to serve WebP image files if accepted by browser (and .webp files available)

apache-webp-rewrite.conf

## !! This snippet has been updated, but not tested in practice. It should work, please check / leave comments in case it doesn't. !! ##

# originally from https://groups.google.com/a/webmproject.org/group/webp-discuss/browse_thread/thread/196ac4ea705688d8
<IfModule mod_rewrite.c>

  # TODO: don't forget to put
  # AddType image/webp .webp
  # in your mods-available/mime.conf
  # (though this is optional because we're setting
  # the mime type manually in the RewriteRule)

  # Enable rewrite 
  RewriteEngine On 

  # Does browser support WebP? 
  RewriteCond %{HTTP_ACCEPT} \bimage/webp\b 

  # Capture image name
  RewriteCond %{REQUEST_URI}  (.*)\.(jpe?g|png)$

  # if you don't have all jpg/png images available
  # as webp then you want to uncomment the next line
  # so apache first checks if there is a webp file
  # otherwise leave it disabled as it removes the
  # need to query the disk
  #RewriteCond %{DOCUMENT_ROOT}%1.webp -f

  # Route to WebP image 
  RewriteRule .* %1\.webp [L,T=image/webp]
  
  <IfModule mod_headers.c>
    <FilesMatch "\.(jpe?g|png)$">
      Header append Vary Accept
    </FilesMatch>
  </IfModule>
</IfModule>