With Firefox’s Reader View, you can read articles on the web like reading a book. The Reader View feature removes buttons, adverts, and images from the page. It also changes the font size and page layout to improve readability.
Access reader mode in Firefox
If a page is available in Reader View, the Reader View 
icon will appear in the browser address bar.
Click the Reader View icon and it will turn blue indicating that the Reader View is active.
To exit Reader View, click the exit icon in the top left corner. You can also find other options to change font size, text-to-speech, and Firefox Pocket.
