A quick doube-tap on Shift does the trick on iPhoneThose of you wondering on how to enable Caps Lock feature on iPhone, here's a quick rundown:

  1. Turn on Caps Lock from the Settings > General > Enable Caps Lock:

    Enabling Caps Lock from the iPhone Settings

  2. Return to your application, double-tap Shift so it turns blue and there you have the Caps Lock in iPhone:

    Caps Lock in iPhone Notes