Devices with -webkit-min-device-pixel-ratio: 1.0
   All non-Retina Macs
   Apple iPhone (1st generation)
   Apple iPhone 3G
   Apple iPhone 3GS
   Apple iPad (1st generation)
   Apple iPad 2
   Apple iPad mini (1st generation)
   Acer Iconia A500
   Samsung Galaxy Tab 10.1
   Samsung Galaxy S
Devices with -webkit-min-device-pixel-ratio: 1.3
   Asus MemoPad HD 7
   Google Nexus 7 (2012 model)
Devices with -webkit-min-device-pixel-ratio: 1.4
   Nokia Lumia 520
Devices with -webkit-min-device-pixel-ratio: 1.5
   Google Nexus S
   HTC Desire
   HTC Desire HD
   HTC Incredible S
   HTC Velocity
   HTC Sensation
   Kindle Fire HD
   Samsung Galaxy S II
   Sony Xperia Tablet Z
   Sony Xperia U
Devices with -webkit-min-device-pixel-ratio: 2.0
   All Macs with Retina displays
   Apple iPhone 4
   Apple iPhone 4S
   Apple iPhone 5
   Apple iPhone 5c
   Apple iPhone 5s
   Apple iPhone 6
   Apple iPad (3rd generation)
   Apple iPad 4
   Apple iPad Air
   Apple iPad mini (2rd generation)
   HTC One X
   Google Galaxy Nexus
   Google Nexus 4
   Google Nexus 7 (2013 model)
   Google Nexus 10
   Motorola Moto X
   Samsung Galaxy S III
   Samsung Galaxy Note II
   Sony Xperia S
   Sony Xperia T
   Devices with -webkit-min-device-pixel-ratio: 2.6
   Nokia Lumia 930
Devices with -webkit-min-device-pixel-ratio: 3.0
   HTC One (M7)
   HTC Butterfly
   Huawei Honor 6
   Apple iPhone 6 Plus
   LG G2
   Nexus 5
   OnePlus One
   Oppo Find 7 (X9076)
   Samsung Galaxy S4
   Samsung Galaxy Note 3
   Samsung Galaxy Note 4
   Sony Xperia Z
   Xiaomi Mi 3

http://bjango.com/articles/min-device-pixel-ratio/