When Google drops support for an iOS version, they do not leave a legacy version on the App Store. The company uses a technique called —if you have iOS 12, the App Store simply refuses to serve you the app. Even if you previously downloaded YouTube years ago, the "last compatible version" prompt has likely vanished for good.

Installing the official YouTube app on iOS 12 has become difficult because Google now requires for the latest versions . For devices like the iPhone 5s, 6, and 6 Plus that are capped at iOS 12, the official app may often fail to load or show "Update Required". 1. Sideloading YouTube IPAs (No Jailbreak)

If you still intend to use an IPA file or modified application, community developers have established a few specific avenues to restore functionality:

: A pop-up will ask if you want to download the "last compatible version" (likely v17.x or older). Tap Bypass Update Prompt