iOS 11.4 (build 15F5037c) is an official Apple over-the-air update for the iPhone 6, released on 2018-04-02T17:06:55Z. The update package is 262.45 MB. This is a delta (partial) update that requires 11.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: f0f2cd88b964557d294ce5a19d4599fb4f3576fd.zip.