iOS 11.3 (build 15E216) is an official Apple over-the-air update for the iPhone SE, released on 2018-03-29T17:13:08Z. The update package is 1.31 GB. This is a delta (partial) update that requires 10.3.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 0181dce31050f07aa4f56ad22a03e8ae5009a8d8.zip.