Font Size App Extension is a useful tool for iPhone users, developed by Out of Web Site LLC. This app extension integrates with Safari, offering the ability to adjust font sizes on any web page with ease. By tapping the Share icon in Safari, users can access the Font Size, Font Size +, and Font Size - extensions, allowing them to increase or decrease font sizes in 25% increments or adjust line height. The straightforward setup process and intuitive interface make it convenient for users to customize their reading experience effortlessly.

To get started, users simply need to open Safari, tap the Share icon, activate the desired font size extension, and adjust the font size as needed. Font Size App Extension requires iOS 8.0 or higher to function smoothly, providing a seamless browsing experience for users seeking personalized text display options.