You can tap the Reader icon whenever you're reading through an article to activate this mode, but there's also a way to turn it on for all articles on a specific website or all supported articles on the web.
- Open up Safari.
- Navigate to a favorite website like MacRumors.com.
- Click on an article.
- In the navigation bar at the top, where it says "Reader View Available," tap and hold on the icon that looks like three lines.
With this feature enabled, all articles that you click on for a specific website (or all websites if you chose that option) will be displayed in Reader View by default.
You can also use Reader View on the Mac too, and your Automatic Reader preferences for Mac can be accessed by going to Preferences in the Safari Mac app and choosing "Reader" under general. You can also turn Reader on for all articles on a particular webpage by right clicking or clicking and holding on the Reader icon while visiting a website.