It does not have WiFi. Currently only the Canon 6D and 70D have built-in WiFi. Some of the pro-bodies (1D X and 5D III) have options to add a wireless file transmitter accessory.
Canon is out front on the WiFi feature and while they've only introduced this on two camera bodies, it seems to be popular. I would not be suprirsed if you begin to see it in more camera bodies in the future.
There are some 3rd party products which offer some limited wireless control of a camera and/or wireless file transfer options. Not nearly as nice as the built-in WiFi as you can get in the 6D or 70D -- but depending on your needs it may be enough.
The T4i doesn't have bult-in wi-fi, but it is compatible with the EyeFi card, which will give it wi-fi capability.
"Some of the pro-bodies (1D X and 5D III) have options to add a wireless file transmitter accessory."
Actually not just the "pro" cameras. There are various "WFT" (Wireless File Transfer) modules for all models 20D through 50D, 5D Mark II & III models, as well as all Mark II and later 1D-series models.
The WFT modules have much greater range and capacity than the built-in Wi-Fi on 70D or 6D, as well as the EyeFi card possible with the 60D. Most of the WFT have 100 meter/300 foot or greater range. WFT modules not only allow for file transfer, they also allow remote control of the camera.
The 60D, 70D, 6D cannot be used with any WFT module.
Rebel (xxxd and xxxxD) series are the only ones that don't have built-in and can't be used with any WFT module. Some of the more recent ones might be EyeFi compatible, I dunno anything about that. I also don't know anything about third party options.
If you are simply wanting to control the camera remotely, there are various possibilities for that.... Though some will need to be wired.
I wanted the WiFi to access media from my camera to a tablet. The EyeFi cards look pretty sweet...I'm just not sure if it's reliable and they are a bit pricey. Maybe I could just use an adapter and transfer that way.
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