This page will show you how to use the command line to start Firefox with a specific window size.
The following command is an example of, how to start Firefox with a specific window size and open the homepage of Firefox. A screenshot of the Firefox window will be 1200×1000, because window decoration is expected to add 2 pixels in each direction.
$ firefox -width 1198 -height 998 https://www.mozilla.org/en-US/firefox
This page was last updated 2021-03-21.