Laptop 1 has bookmark //a.html Laptop 2 has bookmark //b.html Both devices log in with bookmark sync turned on. Q1. Do both devices now have bookmarks a and b? Q2. Laptop 1 deletes bookmark a. Does that delete bookmark a from device 2? Q3. Laptop 1 adds //c.html. Does that add c to device 2? It would be very nice if mozilla would officially explain what happens when bookmarks are synced. Just saying that they are synchronized does not explain what happens. Synchronization can be accomplished in multiple ways.