I, like others who have posted similar questions, have been driven mad that PDFs are downloading to my PC when in the past, they just opened in a new window. I followed the troubleshooting steps posted in this community to ensure that "Preview in Firefox" appears as a drop-down (it did not originally) and that it was selected. (Steps involved getting a cleaned up version of mimeTypes.rdf and handlers.json.) Still, when I click on a the link I was testing this with, it asks me "What should Firefox do with this file?" and if I manually select "Open with...Other...Firefox," it will open in Firefox but still download to my PC. Am I right that the user experience should always be that it automatically opens a new tab and displays the PDF there while NOT downloading to the user's PC? That being said, I tested another random PDF and it did what it was supposed to. I only tested these 2 after I did the fixes so I don't have a high sample size to say if it mostly works or mostly doesn't. There was no discernible difference between the two files: both of their extensions were "pdf," they both had kind of long filenames, and they both had ~100 pages in their files. I would like to get away from downloading files I: 1) don't want to keep and 2) don't trust on my PC but want to read. Thanks in advance!