Apple has finally released public version iOS 9.3 for iPhone, iPad and iPod Touch after seven beta releases for developers from January 7th.
Update iOS 9.3 is one of the biggest updates iOS 9 and includes several new features such as Night Shift mode. This mode uses the device clock iOS and geolocation to automatically change the colors on the display to a warm spectrum, to reduce exposure to bright blue light, to reduce its exposure to your eyes. This mode can also be enabled or disabled from the Control Center.
System iOS 9.3 also includes the ability to set up password or touchID protection for your notes in the Notes app, an updated News app. Added new 3D Touch actions for standard apps such as weather, settings, compass, health, App Store and iTunes Store, the ability to duplicate live photos to still static images, the Health app has been improved, support has been added Apple Music in CarPlay and the new Classroom app, which includes the ability to manage multiple Apple IDs for iOS devices, allowing multiple students to use one and the same device with individual profiles. iOS 9.3 also received Wi-Fi calling support for Verizon subscribers.
You can read more about all the new products iOS 9.3 in this article:
https://it-here.ru/apple/15752/
If you are waiting for a jailbreak iOS 9.2.1 or iOS 9.2 you should not update to iOS 9.3, as it is not yet known for which version the jailbreak will be released. 
But if you are not a fan of jailbreak, then you can install iOS 9.3 via OTA update (over the air) by going to Settings> General> Software Update. The OTA update size on iPhone 6s Plus is 312MB.
If you did not receive the update iOS 9.3 over the air, then you can download the IPSW file iOS 9.3 and update your device manually via iTunes:
Download iOS 9.3 IPSWfor iPhone
iOS 9.3 (iPhone 4S): iPhone 4,1_9.3_13E233_Restore.ipsw
iOS 9.3 (iPhone 5 GSM): iPhone 5,1_9.3_13E233_Restore.ipsw
iOS 9.3 (iPhone 5 GSM + CDMA): iPhone 5,2_9.3_13E233_Restore.ipsw
iOS 9.3 (iPhone 5s GSM): iPhone 6,1_9.3_13E233_Restore.ipsw
iOS 9.3 (iPhone 5s GSM + CDMA): iPhone 6,2_9.3_13E233_Restore.ipsw
iOS 9.3 (iPhone 5c GSM): iPhone 5,3_9.3_13E233_Restore.ipsw
iOS 9.3 (iPhone 5c GSM + CDMA): iPhone 5,4_9.3_13E233_Restore.ipsw
iOS 9.3 (iPhone 6+): iPhone 7,1_9.3_13E233_Restore.ipsw
iOS 9.3 (iPhone 6): iPhone 7,2_9.3_13E233_Restore.ipsw
iOS 9.3 (iPhone 6s): iPhone 8,1_9.3_13E234_Restore.ipsw
iOS 9.3 (iPhone 6s Plus): iPhone 8,2_9.3_13E234_Restore.ipsw
iOS 9.3 (iPhone SE): iPhone 8,4_9.3_13E233_Restore.ipsw
Download iOS 9.3 IPSW for iPad:
iOS 9.3 (iPad 2 Wi-Fi): iPad 2,1_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad 2 GSM): iPad 2,2_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad 2 CDMA): iPad 2,3_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad 2 New): iPad 2,4_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad 3 Wi-Fi): iPad 3,1_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad 3 CDMA): iPad 3,2_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad 3 GSM): iPad 3,3_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad Mini Wi-Fi): iPad 2,5_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad Mini GSM): iPad 2,6_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad Mini CDMA): iPad 2,7_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad 4 Wi-Fi): iPad 3,4_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad 4 GSM): iPad 3,5_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad 4 GSM_CDMA): iPad 3,6_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad Air Wi-Fi): iPad 4,1_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad Air Cellular): iPad 4,2_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad Mini 2 Wi-Fi): iPad 4,4_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad Mini 2 Cellular): iPad 4,5_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad Air China): iPad 4,3_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad Mini 2 China): iPad 4,6_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad Mini 3 Wi-Fi): iPad 4,7_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad Mini 3 Cellular): iPad 4,8_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad Mini 3 China): iPad 4,9_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad Air 2 Wi-Fi): iPad 5,3_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad Air 2 Cellular): iPad 5,4_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad Mini 4 Wi-Fi): iPad 5,1_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad Mini 4 Cellular): iPad 5,2_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad Pro Wi-Fi): iPad 6,7_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad Pro Cellular): iPad 6,8_9.3_13E233_Restore.ipsw
iOS 9.3 (iPad Pro 9.7 Wi-Fi): iPad 6,3_9.3_13E234_Restore.ipsw
iOS 9.3 (iPad Pro 9.7 Cellular): iPad 6,4_9.3_13E234_Restore.ipsw
Download iOS 9.3 for iPod touch
iOS 9.3 (iPod touch 5G): iPod5,1_9.3_13E233_Restore.ipsw
iOS 9.3 (iPod touch 6G): iPod7,1_9.3_13E233_Restore.ipsw
Check out the full list of new features and improvements iOS 9.3:
https://it-here.ru/apple/15752/
If you found something new in iOS 9.3, then please write about it in the comments or in our Vkontakte group.