Apple devices take a long time to sync videos and music, and how can I transfer them successfully?

The transfer rate for anything depends solely on your connection speed to the internet. How fast is your connection? (Go to fast.com or speedtest.net to find out).

Do you have a 3rd party VPN installed, even if you are not using it? VPN slows your speed to 25% of your raw data rate. If you do, delete the VPN profile in Settings/General/VPN & Device Management/VPN, then restart your device. Don't just turn it off; delete the profile. Updates sometimes need to have VPN to be removed and reinstalled. If that fixes it, you can try reinstalling VPN, but probably shouldn't.

With respect to music, are you talking about cloud-based synchronization ("Sync Devices" with an iTunes Match or Apple Music subscription)? Or about manual synchronization (from iTunes or the Finder)?

If you are doing manual synchronization, using a cable, note that

• The Lightning ports on older iPhones (like the iPhone 11) can only transfer data at a maximum of USB 2.0 speeds.
• The USB-C ports on newer iPhones are generally limited to USB 2.0 speeds on "plain" or Plus models. Apple has been reserving USB 3.* speeds for Pro and Pro Max models.

"Apple devices take a long time to sync videos and music, and how can I transfer them successfully?: Someone please let me know why Apple devices doesn't sync videos and music in a short amount of time. iTunes was working great and that has been discontinued and a new device is in operation which definitely requires some technical assistance. I have been trying to transfer home videos it took very long time to transfer and two days later they were disappeared."

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Data Transfer Rate:

A. Use your OWN LAN:

Keep this plugged into a wall outlet for power, and be attached to a network(LAN) that is private(esp. that of your own). If connected to a public LAN, then you might get kicked off, if using too much of the data use you are granted --something campgrounds and hotels have a reputation of performing.

B. Videos Disappearing:

Tap on Search (located at the bottom of a Home Screen) and then type [the name] of these "disappeared" home videos. If locally stored or uploaded to iCloud, then they'll show up. So, find the name of the file(If not known), and then type it in there. Do they show?