Technical Tip: Display images on a Web Filter Block page

Images can be added to the Web Filter Block Replacement Message with the Replacement Message tag '%%IMAGE:<image file name>%%'.

When the URL is blocked on the client machine, the browser fetches the image via HTTPS request from FortiGate to appear on the Block page.

If the client does not trust or install the CA certificate, the Block page will not show the image.

To fix this issue, SSL Deep Inspection must be used, and the CA certificate used in SSL Deep Inspection must be installed or trusted on the client machine.

Starting from FortiOS 7.2.4, there is a new enhancement with a new command setting (embed-image) to embed the image with a base64 string:

config webfilter fortiguard
   set embed-image { enable | disable}
end

Relevant article:

New features or enhancements