How would you transmit smell over the web?

Purely speculating with no technical background..

On the sender side, there would need to be a "smell microphone" to inhale and encode smells based on chemical properties. The data can be transmitted over HTTP or another transfer protocol.

On the receiver side, there would be a "smell speaker" (and maybe amplifier) that decodes and exhales the smell.

I can imagine various technical challenges on both ends, specifically chemical analysis and synthesis on a small enough scale to be practical.

EDIT: This page has a history of such attempts, most recently Aromajoin with "the first wearable scent device" in 2016.

https://en.wikipedia.org/wiki/Digital_scent_technology

I don't have a design, but I chime in on everything. I would suggest that your device should be compatible with existing VR headset gear and not too bulky. Maybe partner with Valve for the network access to allow gamers and game developers to integrate with it easily. There must be an open standard that some of this gear uses.

https://www.wired.com/1999/11/digiscent/ (Note the date.)