TL;DR: Yes, a DFU restore will erase your eSIM data by default. However, when prompted by iTunes or Finder during the restore process, you will be given a specific option to "Retain Cellular Plans." If you select this, the operating system is wiped, but your eSIM profiles remain intact.
An eSIM (Embedded Subscriber Identity Module) is a digital SIM that allows you to activate a cellular plan from your carrier without having to use a physical nano-SIM card. In modern iPhones, especially in the US where physical SIM trays have been removed, the eSIM is the only way your phone connects to the network.
If you are attempting to fix a catastrophic software bug by downloading an iOS IPSW file and performing a full DFU restore, the last thing you want to do is accidentally delete your phone number. Calling your carrier to get a new QR code or digital activation push is frustrating and can leave you without service for hours if you do it wrong.
When you put your iPhone into Device Firmware Update (DFU) mode, you are instructing the computer to completely format the NAND storage chip before reinstalling the operating system. This is a much deeper wipe than standard Recovery Mode.
Because eSIMs are stored in a highly secure, isolated enclave on the logic board, Apple built a specific safeguard into the restore process. When Finder or iTunes detects that you are restoring an iPhone with active eSIM profiles, it will halt the process and ask:
"Do you want to erase all data and settings, and keep your cellular plans?"
The biggest mistake is mindlessly clicking "Next" or "Erase" through all the warning prompts in iTunes. If you click "Erase All" when the cellular prompt appears, your eSIM is permanently deleted, and you will have to contact your carrier (AT&T, Verizon, T-Mobile, etc.) to provision a new one.
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