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When you reset an iPhone, my understanding is that the device does not truly get reset to how it was when it exited the factory.

What about with an Android device? Does performing a factory reset on an Android device always reset the device to how it actually left the factory?

I decided to ask this question to help our community generate accurate answers to this other one.

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  • Only the user data partition is reset. The system partition stays and therefore all updates. But this is the same for iPhone. If an app manages to get root permissions e.g. using a vulnerability of the installed system software it can manipulate the system partition and make changes that are persistent to factory reset. – Robert Feb 23 at 18:55
  • android has factory reset protection (FRP) therefore some partitions will survive – alecxs Feb 23 at 18:56
  • @alecxs Thanks. Which partitions? – RockPaperLz- Mask it or Casket Feb 23 at 18:56
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    idk. that differs. frp at least, maybe misc param persist? on mediatek maybe nvram seccfg para proinfo flashinfo? – alecxs Feb 23 at 19:03
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    @acejavelin of course, i am talking about partitions which contain userdata (like frp) or partitions with temp data (like fota/misc) or partitions with device specific data (calibration data, bad blocks info etc) which can survive, i think we can safely exclude partitions which are included in stock ROM. afaik only cache userdata metadata is wiped for sure on factory reset – alecxs Feb 23 at 19:12
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It is the same as an iPhone I believe. A "factory reset" removes all information in the data and user partition, but leaves everything in the system and associated partitions as is. That means if you got an upgrade or update that changed anything in the system partition, it would remain after a "factory reset".

The reality is that a "factory reset" is kind of a misnomer in this case, it's more of a "user reset" than anything else if we were being more accurate.

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  • So that means that if someone installed a malicious ROM on an Android, it would persist after a "factory reset"? – RockPaperLz- Mask it or Casket Feb 23 at 18:59
  • @RockPaperLz-MaskitorCasket Yes, but for this to occur they would need to unlock the bootloader, so there would be evidence of tampering. Most modern phones cannot have their bootloader unlocked though, and without that and root access to the device, the system partition contents cannot be modified. – acejavelin Feb 23 at 19:01
  • Thanks. I haven't installed a custom ROM in a few years. If unlocking the bootloader is required to do this, and most modern Android devices cannot have their bootloaders unlocked, does that mean that custom ROMs are not available on most modern Android devices? – RockPaperLz- Mask it or Casket Feb 23 at 19:03
  • @RockPaperLz-MaskitorCasket Sadly, that is correct. Very few new(ish) devices outside of Google Pixel, OnePlus, some Samsungs and Moto devices, and a few others, allow the bootloader to be unlocked and rooting to occur, and if it does then tampering is evident as once the bootloader is unlocked, it cannot be relocked without flashing a signed factory image (meaning it is stock), so the evidence of tampering is very easy to determine. – acejavelin Feb 23 at 19:06
  • Interesting. Thanks. Does the bootloader need to unlocked for the device to rooted? Also, is there a good list anywhere of which devices allow unlocking the bootloader? – RockPaperLz- Mask it or Casket Feb 23 at 19:08

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