Android - How to scan QR code for WhatsApp Web?

reboot your phone. I did that and the feature is there in the menu.

After rebooting, you may need to click on "chat," not on "calls" or "contacts." Hope that helps.

Update your WhatsApp to the latest version (2.11.498) and you will see the menu option WhatsApp -> Menu -> WhatsApp Web.

I have updated mine and am able to use WhatsApp web with the same menu option.