2020: Still the worst add-on ever. Works on one PC, won't work on the other. They need to fix this.

2019: Spent MANY HOURS over 3 different days trying to get safari to sync bookmarks to firefox, but it just isn't going to happen. The most obtuse instructions ever, not clear at all. If the only way to do this is to add the firefox mobile app to my phone, no thanks. I don't do that with internet explorer, it just syncs naturally with safari. But firefox, not at all. Horrible app.