Hi Andy, a couple versions ago, Firefox desktop users on Mac, Windows and Linux all got the same new unified print experience. Some users have reported that the preview does not generate or takes a long time to generate, but I don't know whether a pattern has been discovered for that.

In your experience, are particular sites or particular kinds of pages/documents much slower than the others?

Regarding the PDF, you are printing a web page to PDF in the native MacOS print dialog, and that is taking a long time to open in Preview after you save it? I don't know why that would, unless of course it's an unusually large file. ??

Thanks for offering your thoughts I never noticed anything that ever made a difference when trying to print using the new unified print experience. It always took a very long time to complete the preview before I could print.

Are other Mac users having similar experiences? My guess is that the new Firefox versions and OSX are not happy together, but that's just a guess on my part.

Regarding creating a PDF from a web page using the System dialog. I just tried creating a PDF from a very short web page. It took a long time before the PDF icon appeared on my desktop. It used to happen very fast before the newer versions of Firefox showed up.

It is interesting that I have slow processing of print preview in the unified version and slow processing of PDF generation in the classic dialog. It seems to me it has to be a bug in Firefox. If that is the case, I wonder if there is any preference or setting that can help resolve this or does Mozilla need to troubleshoot the problem.

The slow printing problem exists with osX Sierra 10.12 and possible other versions prior to 10.14.

The bug has bee reports numerous times but on one is working on a fix as of 10/16/21.

Probably no choice but to switch to another browser.