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.
What Is an eSIM?
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.
Why It Matters
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.
How It Works: DFU Mode and Cellular Data
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.
The "Retain Cellular Plans" Prompt
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?"
Practical Steps
- Step 1: Enter DFU Mode. Connect the iPhone to your computer and perform the required button sequence to enter DFU mode (the screen will remain completely black).
- Step 2: Initiate the Restore. In Finder or iTunes, click "Restore iPhone".
- Step 3: Watch for the Prompt. The software will extract the IPSW file. Right before the installation begins, the prompt will appear. You must actively select the option to keep your cellular plans.
- Step 4: Activation. After the restore finishes, your iPhone will reboot to the "Hello" screen. During setup, the phone will automatically reconnect to the cellular network using the retained eSIM profile.
Common Mistakes
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.