I noticed the other week that some of the image SRC links within my website HTML code was being transformed. Basically a spurious http://220.127.116.11/bmi/ (or a version of this such as 18.104.22.168/bmi/, 22.214.171.124/bmi/ etc) was being injected into my HTML code when my website was being viewed. At first I thought it was my web host implementing some kind of image caching so i ignored it for a while. I then started notice that the images were not always been displayed so I contact them to discus the issue and to find out what was going on.
To cut a long story short it turned out to be my internet service provider(ISP) Three.co.uk. Because it is a 4G mobile based provider they and most of the others seem to use a service call ByteMobile, which tries to reduce the amount of data being transferred. I’m not sure they use this all the time but just in busy areas or at peak times.
After a bit of trial an error the final solution was quite a simple one, just enter the following code into your .htaccess file.
Header set Cache-Control “no-transform”
this then tells the service provider that pages from this website should not be transformed and to display them as they are.
Fix with HTTPS
I believe an alternate fix would be to implement HTTPS on your web site, this way your code is secure and the service provided is unable view or transform it even if they wanted too