Dropbox's Lepton [1][2], an additional lossless compression layer that operates on top of JPEG, would make for a smoother transition.

If a browser natively supported Lepton, you could serve the compressed version over the wire, and still get the bit-exact original .jpg out at the end, if the user wanted to save the file.

Of course, browser support doesn't exist yet. But browser implementors, consider the gains. This isn't promoting an incompatible format, it's getting bandwidth savings while being fully backwards compatible.

[1] https://blogs.dropbox.com/tech/2016/07/lepton-image-compress... [2] https://github.com/dropbox/lepton