Rather than sync my more than 8000 bookmarks on my PC with Safari browser on my iPhone, which would be a total mess, I always used Xmarks Premium. The bookmarks from my PC were contained in the Xmarks app on my iPhone in neat folders exactly as they appear in my PC browser and I could direct them to open in Safari. All was well until I upgraded to iOS 11. I then discovered that Xmarks will not run on iOS 11 and there is no update available. After submitting a problem ticket I received a response saying that they are aware of it, that there are no plans, but that the devs will be looking into it. Whatever that means. Xmarks Premium, is a paid subscription service; annual payment is required to use it on mobile devices. I and many others have paid to have it on our iPhones and iPads. There is a forum and a thread in that forum that is rapidly filling with complaints. If anyone uses Xmarks Premium on an Apple mobile device, I suggest you file a trouble ticket and post on the forum.