This article explains how to block websites on iPhones and how to add or remove sites from an approved list.
How to Block Websites on ANY iPhone! (2022)
The iPhone, iPad, and iPod touch have built-in tools to control which websites children can visit. This feature allows adults to block access to websites, and the settings are protected with a passcode so that a child cannot change them.
From the iPhone home screen, tap Settings.
Select Content & Privacy Restrictions.