For iOS 11 uses, in order to reduce the occupied space of camera videos and photos. In the iOS device Apple used HEIC (High Efficiency Video Coding) high efficiency video encoding technology (also known as H.265), and HEIF (High Efficiency Image File Format) high efficiency picture format.
However, in most situations, this new technology is not supported in operating systems or cloud services, especially for the Windows users and Android users.
Apple will automatically convert HEIC photo files into JPEG files when you transmit photos on App (Twitter, Instagram, Facebook, etc).
When you directly connect iPhone (iOS 11) to PC or Mac, the system will automatically convert the formats of photos and movies too.
Most old versions of PC, Android (Samsung, HTC, Huawei, LG and so on) and iPhone (7/7 Plus/SE/6s Plus/6s/6 Plus/6/5s/5c/5/4s/4) don’t support this technology.
This means that iPhone X/8/8 Plus users can’t transfer photos to devices which are not iOS 11 system. We can’t open these photos!!