Hide distractions when reading articles in Safari on Mac
You can use Safari Reader to view a web page article in one page, formatted for easy reading and presented without navigation or other distractions. You can adjust the background colour, font and font size.
View an article using Reader
In the Safari app
on your Mac, click the Page menu button 
in the Smart Search field, then click Show Reader.The button appears only if the webpage has an article that Reader can show.
To stop using Reader, click the Reader button
in the Smart Search field, then click Hide Reader (or press Esc).
Change how your web pages look in Reader
In the Safari app
on your Mac, while viewing an article in Reader view, click the Reader button that appears at the left end of the Smart Search field.Do any of the following to adjust the settings:
Choose a background theme.
Choose a font.
Choose a zoom level.
Reader always shows you the last background theme, font and size you chose.