To back up an iPhone, there are mainly two reliable methods: using iCloud or using a computer (Mac or PC).

Backing Up with iCloud

• Connect the iPhone to a Wi-Fi network.
• Go to Settings, tap your name, then tap "iCloud."
• Tap "iCloud Backup" and turn on "Back Up This iPhone."
• Tap "Back Up Now" to create a manual backup or let it back up automatically daily when the iPhone is connected to power, locked, and on Wi-Fi.
• Note that 5 GB of free iCloud storage is provided, and more can be purchased if needed.

Backing Up Using a Computer

• On a Mac with macOS Catalina or later, open Finder; on macOS Mojave or earlier, or on a Windows PC, open iTunes.
• Connect the iPhone to the computer with a USB cable.
• If prompted, enter the device passcode and trust the computer.
• In Finder or iTunes, select the iPhone device.
• Choose to back up all data on the iPhone to the computer.
• Click "Back Up Now" to start the backup.
• You can also choose to encrypt the backup for added security, requiring a password to restore.

Each method has its advantages: iCloud is wireless and automatic but limited by storage space; the computer backup stores everything locally, including more data types and media.