Some Apple URL schemes are documented for third-party use. It’s fine to use those URL schemes for their intended purpose. Other Apple URL schemes are not officially documented. Their use is unsupported. If you rely on such implementation details, things might work, or they might not, and that state might change over time. IMPORTANT If you ship via the App Store, pay attention to clause 2.5.1 of the App Review Guidelines. The Apple URL scheme documentation is not always easy to find. I’m aware of the following: Apple URL Scheme Reference QA1924 Opening Keyboard Settings from a Keyboard Extension [This Q&A was retired years ago.] Preparing your app to be the default messaging app The doc comments for es_new_client in Developer > Bug Reporting describes the applefeedback scheme Additionally, as questions about this most commonly crop up in the context of opening Settings (System Settings on macOS), I wanted to highlight the following: UIApplication.op