iOS 8.3 (build 12F70) is an official Apple over-the-air update for the iPhone 6+, released on 2015-04-08T17:56:16Z. The update package is 598.44 MB. This is a delta (partial) update that requires 8.0.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: ecc251744483761b523253c0ae958856f646f8c3.zip.