there's some issues and it still works for many sites and apps including the basic basic HTML version of Gmail including gitlab including many news sites.
I find it saves my bandwidth literally about 10 to 20 times. for example if normally browser session for a couple of hours would use 200 megabytes of data I can do it with this in anywhere from 10 to 20 megabytes of data.
I don't know if this is a product but it's useful for me (and getting more useful as I fix bugs) and I have plans to improve the data reduction even more.
the version I posted is a paid version so I'm including this link to one that you can try out without paying and just using a stripe test card.
test card version: https://staging.stretchy.live (if you don't want to go through the lengthy signup process, just login with username/password: hacker/hacker)
I also want to add that I like how this and extrapolating forward from this, compliments ideas about reducing website bloat in general that are gaining currency at this time.
Safari users on iOS please note: you'll need to turn on Pointer Events in advanced settings.