When Google updates the YouTube app, they typically drop support for older iOS versions to take advantage of new frameworks and security features. If you try to download YouTube from the App Store on an iOS 9.3.5 device today, you will be met with an error requiring iOS 11 or later.

This comprehensive guide covers everything you need to know about finding, installing, and fixing a YouTube IPA for iOS 9.3.5. Understanding the iOS 9.3.5 YouTube Problem

Are you seeing a (e.g., "403 forbidden" or "unable to purchase")?

Enter the IPA. These are modified versions of the official YouTube application, injected with code—often based on the open-source Cercube or YouTube++ tweaks—that unlocks features Google never intended for iOS.