How does Chrome's "Request Desktop Site" option work?

Question

For iOS google chrome, when a user hits the "Request desktop site" button what does the browser do to try to bring up a desktop site? I imagine some sort of header on the request that sites are looking for, or something similar?

Answer 1

I think the only difference is the User-Agent: header in the request.

Here are the User-Agent headers sent by Chrome on my Android device:

Mozilla/5.0 (Linux; Android 4.0.4; Galaxy Nexus Build/IMM76K) AppleWebKit/535.19 (KHTML, like Gecko) Chrome/18.0.1025.166 Mobile Safari/535.19  Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/535.19 (KHTML, like Gecko) Chrome/18.0.1025.45 Safari/535.19 

Notice the word "Mobile' in the first one, and also the mention of Android system and device. Checking these, I see that it also provides false information - namely X11 and x86_64 - to closely match the value sent by the Desktop Linux version of Chrome.

Answer 2

Just wanted to point out that Chrome now not only changes the User-Agent but also ignores the original viewport meta tag if you "Request Desktop Site". Thus it won't be necessary to sniff the User-Agent anymore and you can rely on the viewport change as most responsive sites will automatically do. See this Change for further reference.