TL;DR
- A factory reset erases the user data partition and restores the OS to its default state; on modern encrypted phones, residual fragments are cryptographically inaccessible.
- A reset alone is not sufficient: you must also sign out of your Apple ID or Google account to lift activation lock, or the new owner will be unable to activate the device.
- Remove the physical SIM card before handing over the phone — a reset does not touch the SIM, which holds your mobile number and may store contacts or short messages.
- On iOS, use Settings > General > Transfer or Reset iPhone > Erase All Content and Settings; on Android, the path varies by manufacturer but is generally Settings > General Management > Reset > Factory Data Reset.
- Any SD card inserted in the device must be removed or separately formatted; the device reset process does not reliably wipe removable storage.
What a factory reset actually does
A factory reset is a software instruction that deletes the user data partition on a device’s internal storage and reinstalls or reactivates a clean copy of the operating system. The effect from the user’s perspective is that the phone returns to the state it was in when it left the factory: no apps beyond the pre-installed set, no accounts, no messages, no photographs, no saved passwords. The process is initiated through the device’s own settings menu and typically takes between five and fifteen minutes depending on how much data needs to be cleared.
On devices running Android 6.0 (Marshmallow) and above, internal storage is encrypted by default using AES-256 or equivalent. When a factory reset is performed, the encryption keys stored in the Trusted Execution Environment (TEE) are discarded. This means any data remnants that might technically persist in flash storage cells after the reset are rendered permanently unreadable without the key, even using forensic tooling. Apple’s iPhones have operated on a similar principle since the introduction of the Secure Enclave with the iPhone 5s in 2013. For phones predating these architectures — which are now very old — additional steps such as re-encrypting before resetting were advisable, but for any handset in common circulation today the standard reset process provides robust data protection.
What a factory reset does not do
Three categories of data are not affected by a device factory reset and require separate action. First, the SIM card is entirely independent of the phone’s storage and is not touched by the reset process. A SIM can hold contacts and SMS messages in its own internal memory, and it carries your mobile number as a physical credential. You should physically remove the SIM tray and retain the card before handing the phone over.
Second, any removable SD card inserted in the device is not reliably wiped by a factory reset. Most Android device reset menus offer the option to include the SD card in the wipe, but the behaviour varies by manufacturer and Android version. The safest approach is always to remove the SD card separately and either reformat it on a PC or retain it. Third, cloud-linked accounts — iCloud, Google, Samsung, or any third-party service — remain active on the servers even after the phone is reset. The data stored in the cloud does not disappear when you wipe the handset; you must sign out of and, if appropriate, remove the device from those accounts through their respective web interfaces before performing the reset.
Signing out of accounts and disabling activation lock
Both Apple and Google implement an activation lock mechanism that ties a device to the owner’s account and prevents it being set up by a new user if the lock remains active. On an iPhone, this is called Activation Lock and is linked to the Apple ID via Find My. If you sell a phone without signing out of iCloud and disabling Find My, the buyer will be presented with an Apple ID login prompt they cannot bypass — effectively making the device unusable. The correct procedure on iOS is to go to Settings, tap your name, scroll to the bottom and select Sign Out, and confirm. This automatically removes the phone from your iCloud account and disables Find My and Activation Lock.
On Android, Google’s equivalent is Factory Reset Protection (FRP), which activates when a phone is reset while a Google account is signed in. After a reset protected by FRP, the phone requires the previous Google account credentials to activate. To avoid this issue for the buyer, sign out of your Google account before initiating the reset via Settings > Accounts > Google > Remove Account, or sign out and then perform the reset. Samsung devices have an additional layer through Samsung Account which should also be removed via Settings > Accounts and Backup > Manage Accounts. Failing to address these locks is one of the most common causes of dispute in second-hand phone transactions.
How to perform the reset on Android and iOS
The exact menu path on Android varies between manufacturers and Android versions, but the universal route is to open Settings, search for “reset” using the search bar at the top of the Settings app, and select Factory Data Reset or similar. The phone will typically display a warning listing what will be deleted, prompt for a PIN or biometric confirmation, and then proceed with the wipe. Some manufacturers require the process to be initiated twice to confirm. The device will reboot and display the initial setup wizard when the reset is complete.
On an iPhone or iPad, navigate to Settings > General, scroll to the bottom, and select Transfer or Reset iPhone. Choosing Erase All Content and Settings initiates a process that verifies your Apple ID credentials (if Find My is enabled), downloads the latest erasure algorithm from Apple’s servers if connected to Wi-Fi, and then performs the wipe. The Secure Enclave discards the encryption keys at this point, and the device reboots to the Hello screen. On older iOS versions without the Transfer or Reset interface, the equivalent path was Settings > General > Reset > Erase All Content and Settings.
| Step | Action | iOS path | Android path (general) |
|---|---|---|---|
| 1 | Back up data | iCloud Backup or Finder/iTunes | Google One Backup or manual transfer |
| 2 | Sign out of primary account | Settings > [Your Name] > Sign Out | Settings > Accounts > Google > Remove Account |
| 3 | Remove SIM card | Eject SIM tray with tool | Eject SIM/SD tray with tool |
| 4 | Remove or wipe SD card | N/A (iPhones have no SD slot) | Remove or format via Settings > Storage |
| 5 | Perform factory reset | Settings > General > Transfer or Reset iPhone > Erase All Content and Settings | Settings > General Management > Reset > Factory Data Reset |
| 6 | Verify device shows initial setup screen | Hello screen displayed | Language/Wi-Fi setup screen displayed |
What happens to your accounts after a factory reset
Signing out of your Google or Apple account before the reset removes the device from the account’s registered list, but your account itself, and all data stored in the cloud associated with it, remains entirely intact. Your Gmail, Google Photos, Google Drive, iCloud Mail, iCloud Photos, and any other cloud data are stored on the provider’s servers, not on the phone. They will be accessible again from any other device or browser using your credentials. The reset and sign-out process only removes the device’s local copy of that data and its authorisation to access the account without credentials.
What this means in practice
Marcus, a fictional seller in Bristol, lists his two-year-old Android smartphone on an online marketplace. Before posting the listing, he backs up his photos to Google Photos and checks his Google One backup is current. He opens Settings, taps Accounts, removes his Google account, and also removes his Samsung account. He pops out the SIM tray, keeps the SIM, and notes there is no SD card in this particular model. He navigates to Settings > General Management > Reset > Factory Data Reset, enters his PIN, confirms, and waits approximately eight minutes for the phone to restart. The screen shows the initial language selection, confirming the reset was successful. He photographs the setup screen as informal evidence before posting the phone. The buyer activates the device without any FRP prompt because the Google account was removed prior to the reset.
Related Guides
How we verified this
This article draws on ICO guidance on personal data and device disposal published on ico.org.uk, Apple’s published support documentation on Activation Lock and the Secure Enclave (referenced for technical description only), Google’s published documentation on Factory Reset Protection, the Android Open Source Project security documentation regarding encryption, and the ICO’s UK GDPR accountability guidance.
Disclaimer: Kaeltripton.com is an independent UK editorial publisher. We are not regulated by Ofcom or the FCA and we do not sell or arrange mobile services, insurance, or financial products. This content is for general information only and is not legal, financial, or technical advice. Rules, prices, and operator policies change. Verify the current position with Ofcom, GOV.UK, the ICO, or your provider before acting. ICO registered ZC135439. Last reviewed: 2026-06-05.
Frequently Asked Questions
Does factory reset delete everything?
A factory reset erases the user data partition and removes all apps, accounts, photos, messages, and settings you have added since the phone was new. On modern encrypted devices, encryption key destruction means residual data fragments are unreadable. However, it does not touch the SIM card, removable SD cards, or data held in cloud accounts. You must also sign out of your Apple ID or Google account beforehand to disable activation lock, which is a separate process from the reset itself.
How do I factory reset an Android phone?
The most reliable path across Android manufacturers is to open Settings and search for “reset” using the built-in search bar. Select Factory Data Reset (or the equivalent on your manufacturer’s version, such as “Erase all data”). On Samsung devices the path is typically Settings > General Management > Reset > Factory Data Reset. You will be asked to enter your PIN and confirm. The process takes several minutes and the phone will reboot to the initial setup screen when complete. Ensure you have signed out of your Google account first to prevent Factory Reset Protection blocking the next user.
How do I factory reset an iPhone?
On current iOS versions, go to Settings > General, scroll to the bottom, and tap Transfer or Reset iPhone, then choose Erase All Content and Settings. If Find My is enabled, you will be asked to enter your Apple ID password to confirm; this simultaneously disables Activation Lock. On older iOS versions, the equivalent option is at Settings > General > Reset > Erase All Content and Settings. The phone will reboot to the Hello screen when the process is complete. Ensure you have a current iCloud backup beforehand if there is data you wish to retain.
Should I remove my SIM before selling my phone?
Yes, always remove your SIM card before handing over any phone. A factory reset does not touch the SIM, which contains your mobile number as a physical credential and may store contacts or text messages depending on your settings. If you use an eSIM, follow your operator’s process to delete or transfer the eSIM profile before the sale. Keep the removed nano-SIM card safely, or if upgrading networks, request a port of your number to a new SIM from your new operator before disposal.
What happens to my accounts after a factory reset?
Your cloud accounts — Google, Apple ID, Samsung, and any third-party services — are stored on remote servers and are completely unaffected by a factory reset on the device. All your contacts, photos, emails, and app data remain accessible from other devices or via a web browser using your login credentials. The reset removes only the device’s local copy of that data and its stored authorisation. Your account itself, and everything in it, continues to exist exactly as before.
