iOS 8.3 (build 12F5061) is an official Apple over-the-air update for the iPhone 6+, released on 2015-03-24T16:54:15Z. The update package is 146.34 MB. This is a delta (partial) update that requires 8.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 5124450dd0a3f51c3395ec51406dd8b2652672eb.zip.