If you are the owner of a compatible iPhone, iPad, or iPod touch, then you can grab the latest update as an over-the-air update via Settings > General > Software Update. Alternatively, you can grab the IPSW download for your device from the links below
Release Date : Wednesday, December 5, 2018
Upload Date : Wednesday, December 5, 2018
Filename : iPhone10,3,iPhone10,6_12.1.1_16C50_Restore.ipsw
Filesize: GB 3.33
MD5sum : 774acb0e8a7289b21a81111b3db58f05
SHA1sum : bbe8d7640d4f88ef107ed3c529ed2b1d1e44332c
link Download ios 12.1.1