Is there a way to resize a web browser's window so that their dimesions are a specific width and height?

Question

I need to view a webpage using specific dimensions without having to resize a web browser window all the time.

Answer 1

(Windows)

Firefox:

• Shortcut: Ctrl+Shift+M, or:
• Press F12 to open devtools sidebar
• On the top right corner of the bar, click the button "Responsive Design-modus", the icon looks like a little phone on a tablet

Chrome/ Edge:

• Shortcut: Ctrl+Shift+M, or:
• Press F12 to open devtools sidebar
• On top left corner of the bar, click the button "Toggle device toolbar", the icon looks like a phone on a tablet (Chrome) or a phone on a screen (Edge)

Opera:

• Shortcut: Ctrl+Shift+M (might not work and open Messenger sidebar by default), or:
• Press Ctrl+Shift+I to open devtools sidebar
• On top left corner of the bar, click the button "Toggle device toolbar", the icon looks like a phone on a tablet

How to use:

• From the dropdown menu "Responsive" you can change the viewport size to match a set of devices or add your own, or leave it on responsive and change the two number fields next to it with the desired width and height