Firefox stores separate scaling, paper size, margin, and other settings per printer, so that could explain part of the difference.

Also, there is something wrong with shrinking the page below 94% on Firefox 90 -- whether Firefox does it with Shrink to Fit or you set the scaling manually. Here's another thread about that:

https://support.mozilla.org/en-US/questions/1343808#answer-1427683

I'm going to see whether I can track down the source of that problem...

Several bug reports have been filed. Hopefully we'll get a fix or some kind of workaround soon.

Thanks Jefferson, I see that you open a bug report here https://bugzilla.mozilla.org/show_bug.cgi?id=1720622

Hope this will be fixed soon ¡¡¡

The 90 version has a couple of printer problems. First, it does not retain the last target printer used, nor does it just revert to the Windows default printer, but instead appears to just randomly choose any printer in the list.

Worse, is even if the preview looks correct, it does not output correctly to any of type printer regardless of the settings, as it cuts off the right side of the page, and no adjustments fix it.

All other browsers work fine, and reverting to the previous version of Firefox also restores proper printing.

The scaling bug -- cut off content -- is already on file.

I don't know why the printer would not be remembered, though, I have not experienced that problem.

A Firefox update (Firefox 90.0.2) has been released to fix this printing bug in Firefox 90. Release notes: https://www.mozilla.org/en-US/firefox/90.0.2/releasenotes/ (quote) Fixed truncated output when printing (bug 1720621)