When restoring data, you will be asked if you want to join or replace data.

Before I activate Firefox Sync on my 2nd computer (one that is running a different Mac OS) I want to know if the Firefox bookmark list on that 2nd machine will be merged or will the file be overwritten by the file that is now stored on the Mozilla servers. I'm not sure how to translate your response into my language and for my circumstance.

I am not restoring data on either computer. I'm asking what will happen when I activate Sync on a 2nd computer. I was not given any option to "join or replace data" when I activated Sync on the 1st computer. I still do not feel comfortable about activating Sync on the 2nd computer since I'm not sure what it will do.

Firefox 30.0 is on both 1st & 2nd computers. 1st is running Mac OS 10.6.8 and 2nd is running Mac OS 10.9.4.

I do not use it myself. Some users have reported problems using the service.

If you want to keep your information safe, try these;

These add-ons can be a great help by backing up and restoring Firefox

FEBE (Firefox Environment Backup Extension) {web link} FEBE allows you to quickly and easily backup your Firefox extensions, history, passwords, and more. In fact, it goes beyond just backing up -- It will actually rebuild your saved files individually into installable .xpi files. It will also make backup of files that you choose.

OPIE {web link} Import/Export extension preferences

The currently used Sync version always merges data and you can no longer set via the Sync options how to do the first sync.

Note that it is always best to backup your profile data locally.

• https://support.mozilla.org/kb/Backing+up+your+information

Well, I used the Mac OS to create backup copies of the Profile folder in another location on my HD and then initiated Sync on the 2nd computer. It appears to have gone off without a hitch, merging the bookmarks files from 2 different computers.

Thank you very much.