How do we know if your iPhone 5s is fake or real?

How do we know if your iPhone 5s is fake or real?

If you buy it from a proper retailer, it is very likely it is real. Avoid buying off ebay/similar sites, as these kinds of sites are more likely to be selling fakes.

It should have a logo

Just use it and you'll see. Is it a fast and fluid, smooth experience? Does it have iOS 7? A quick look and some exploration in Settings will show you. It should've asked you for your Apple ID and can you create a Touch ID using it? Are the icons de-skeumorphed and made flat copying the Windows Phone style but hideously? If the answer to most of these questions is yes, you're with a real one.

If it is running iOS or not. Because of iOS's closed source no fake can run it.

As has been mentioned look at legit sites to purchase. If it is too good to be true (price) it usually is.

If the site is something like allnewiphonesboughtreallyreallycheap.com then you are probably getting scammed.

Compare everything with the official specs on Apple's official site.