Best answer: Unfortunately, no, you can't use your old iPhone case with an iPhone 11. The iPhone 11 has a brand new dual rear camera setup that means that old cases won't fit. Instead, you'll need to get something like the URMax iPhone 11 case.
Keep your new iPhone safe: URMax iPhone 11 case ($9 at Amazon)
Your old case won't fit the iPhone 11 because of the camera
The new camera system on the back of the phone is the primary reason that your old case won't fit the iPhone 11. Instead of a single lens, or a dual-camera pill-like structure (like the iPhone X and XS), there's a big ol' square with two lenses on it dashing any of your case-transferring hopes.
The iPhone 11 (not to mention the iPhone 11 Pro) has the largest camera bump ever on an iPhone. The phone now sports both a standard wide-angle camera, as well as a super-wide camera for zooming way out. Having both cameras enables improvements in Portrait mode photography, but at the cost of being able to use an older case.
Interestingly, if it wasn't for the camera bump, the iPhone 11 would theoretically be able to fit cases made for the iPhone XR, as the two devices are the same thickness, width, and height.
There are great cases for the iPhone 11 out already
Though the iPhone 11 was recently announced, there are a number of cases already on sale for Apple's newest phones. Cases like the URMax iPhone Case are low-cost while still providing excellent protection, and you can get them delivered fairly quickly so they might even be on your doorstep by the time your iPhone arrives.
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