You need to know whether or not Apple’s iCloud is syncing your bookmarks. The answer is YES if and only if iCloud:Safari is switched ON in a given device.
On iOS Devices
• Run the Settings app into its first screen.
• In the left column, at the top, if it says Sign in to your iPhone/Pad, then iCloud:Safari syncing is OFF. If not, continue…
• Click the top item which has Your Name and then Apple ID, iCloud….
• In the right column, navigate into iCloud.
• Under APPS USING ICLOUD, the state of iCloud:Safari syncing is the state of the Safari checkbox.
(The above is for iOS 10.3.3 or later. Earlier versions, the iCloud item was in the left column of the first screen.)
On your Mac Devices
• In your menu bar, click the apple > System Preferences. An array or preferences will appear.
• Click the iCloud:
• See if the checkbox for Safari is switched on.
If your checkbox is ON, the answer is yes. If your checkbox is OFF, it is no.
If you are using macOS 10.12 - 10.13.2, read on…
When you switch the checkbox OFF in macOS 10.12 - 10.13.2, syncing ceases as expected, but the checkbox usually switches itself back on again after about 1 second. So it looks like syncing is still ON when actually it is OFF. Conversely, if you switch it ON, and then OK the merge, it will sometimes, but not always, switch itself OFF, so that it looks like syncing is OFF when actually it is ON.
We have found the following workaround: After you change the checkbox from OFF to ON or ON to OFF, you should quit System Preferences, then relaunch System Preferences and inspect the checkbox you just changed. If it is the same as before you quit, you are done. If it has changed, change it back to the way you want it, then repeat the quit, relaunch and inspect again. It should work on the second try.
It appears that Apple has fixed this bug in macOS 10.13.3, which will probably be pushed out to all users some time this month (January 2018).