How to erase everything on iphone before trade in

For a modern iPhone, the built-in "Erase All Content and Settings" function is considered the gold standard for securely and permanently erase everything on iPhone before trade in. This is because modern iPhones utilize hardware encryption: all user data is encrypted by default using a unique key stored in a dedicated part of the device's chip.

When you perform the factory reset through the Settings menu, the operating system doesn't actually overwrite every bit of data on the storage chip (which would take hours). Instead, it instantly and cryptographically deletes the encryption key needed to decrypt the data. Without this key, the raw data remaining on the device is rendered permanently inaccessible and unrecoverable, even by sophisticated forensic tools.

However, the main risk associated with a simple "factory reset" on an iPhone is not the data erasure itself, but failing to properly disassociate the device from your Apple ID. If you do not manually sign out of iCloud before initiating the reset, the device remains locked via Apple's Activation Lock/Find My feature. This prevents any new owner or trade-in partner from activating or using the phone, which will automatically result in a rejected trade-in.