-
Get the profile folder location in
about:supportpage -
Edit the file
xulstore.jsonfound in the above folder. It's a json file and we need only to edit the keymain-windowto something like this:
"main-window":{"screenX":"0","screenY":"0","width":"1920","height":"1080","sizemode":"maximized"}
NOTE:
- Step 2 should be done when Firefox is not open, as it seems that the file get updated when Firefox closes.
- Sometimes you need to put negative value to
screenXif the windows is still shifted abit from the screen edge.