With Safari 9.0, Apple introduced a new mode that allows Safari to mimic how a website might preview on various mobile devices. It is just a preference you have to turn on in your preferences.
Here’s how to turn on Responsive Design Mode in Safari:
- Go to Safari > Preferences
- In the Advanced tab, click on Show Develop menu in menu bar.
- You should now have a new option available in your Safari menu bar.
- Under the Develop menu in your Safari menu bar, select Enter Responsive Design Mode.
This will allow Safari to mimic what a site looks like on various devices (an example is shown below).
Note: You have to be viewing a web page in order to select Enter Responsive Design Mode in the Develop menu. If you are viewing Safari’s default start page, Enter Responsive Design Mode will be greyed out.