Webp images loaded on non compatible browsers

this is most likely if you have additional cache layer

please provide the report number , you can get it in toolbox -> report -> click “send to LiteSpeed”

Thank you !
Here is the report number : DYLWAQKL.

If this can be related to an additional cache layer, then you should know that I always have to empty all cache entries (the last button from the toolbox menu) if I change a CSS file, otherwise the new file is not loaded if I just hit the “Purge all” button.

you are using LiteSpeed ADC , I assume it’s from o2switch

in this case , you will need to ask your provider , to copy-paste the webp vary rule

### marker WEBP start ###
RewriteCond %{HTTP_ACCEPT} "image/webp" [or]
RewriteCond %{HTTP_USER_AGENT} "Page Speed"
RewriteRule .* - [E=Cache-Control:vary=%{ENV:LSCACHE_VARY_VALUE}+webp]
RewriteCond %{HTTP_USER_AGENT} iPhone.*Version/(\d{2}).*Safari
RewriteCond %1 >13
RewriteRule .* - [E=Cache-Control:vary=%{ENV:LSCACHE_VARY_VALUE}+webp]
### marker WEBP end ###

this section from your .htaccess, into ADC’s vhost rewrite rule , in order to make ADC to be able to vary the cache for webp

Yes indeed, I am hosted by O2Switch.
I asked them to add these lines but unfortunately they are not able to do it. They told me that the configuration on the litespeed side is not changeable at the moment and that they have the impression that it impacts the overall configuration.

Is there another way to make it work or should I disable the webp feature ?

well , unfortunately , that’s the only way ??