Some browsers have built in support to test websites across different device widths/heights.
Firefox refers to it as their "Responsive Design Mode" and Google Chrome refers to it as "Device Mode".
With this mode enabled, a user can simulate viewing a website on a mobile device or tablet.
- For Google Chrome, refer to: https://developers.google.com/web/tools/chrome-devtools/device-mode/
- For Firefox, refer to: https://developer.mozilla.org/en-US/docs/Tools/Responsive_Design_Mode