Ubuntu 18.04, CUPS2.2.7, Firefox 69.0.2 I use a custom web application that (among other functions) allows the print of labels. The labels are configured to the size of the label printers (3 printers, two label sizes). When I print the labels to a pdf file (print dialogue, "Print to file"), output with correct orientation, size and content is produced. When I print the these labels from a pdf-viewer to the label printers, output is correct. However, when I print directly from Firefox to the label printers, the output is rotated by 90°. Labels from label printing software (glabels) are also printed correctly. On Windows, this is not an issue and printing works directly from Firefox. Apparently, the problem is caused by Firefox, but restricted to Linux (several computers). Any ideas on how to find the problem are appreciated. Many thanks in advance!