Does a Factory Reset Delete Everything? What Refurbished Sellers Actually Publish
5 min read
German households are sitting on 167 million unused phones. Bitkom asked 1,004 people aged 16 and over on 15 April 2026. 28 percent named one reason: worry that personal data ends up in the wrong hands. So, does a factory reset delete everything? That question is holding a lot of drawers shut.
What a factory reset actually removes
Ordinary deletion only strips out "the references to the data in the index", writes Germany's federal cyber-security agency, the BSI (translated, accessed 13 Aug 2026). On an encrypted device, the same page says erasing all the keys securely is enough.
Apple's wording is blunter. Per Apple's security documentation, erasing "obliterates all the keys in effaceable storage and renders all user data cryptographically inaccessible". NIST SP 800-88 Rev. 1 (2014) calls that a Purge, a level above plain overwriting.
The old fear has a real source. Laurent Simon and Ross Anderson of the University of Cambridge found in 2015 that on all 21 phones they tested with a flawed factory reset, Google credentials could be recovered: five vendors, Android 2.3 through 4.3. Android has supported encryption since 5.0, and full-disk encryption hasn't been allowed on new devices since Android 10.
What the sellers publish about erasure
We compared what the four retailers publish themselves. The difference is stark.
asgoodasnew is the most specific (accessed 13 Aug 2026), naming its software: Blancco removes all data remnants from every device. rebuy promises "certified and professional data erasure" (12 May 2026) without naming software or a standard. refurbed gives the step one sentence: old data is securely deleted and the storage overwritten (accessed 13 Aug 2026). Back Market treats erasure as a by-product of the reset, saying all devices are reset to factory settings, "which means the data is securely removed" (accessed 13 Aug 2026). All four quotes are translated from German.
Four retailers, four levels of detail. That's all you can check before ordering. How the platforms differ elsewhere sits in our Back Market, Refurbed and Rebuy comparison.
The check on arrival takes under a minute. The device has to boot into first-time setup. If it asks for somebody else's Apple Account or Google account, it wasn't prepared properly. Don't sign in. Message the seller first. Our refurbished iPhone buying checks cover the rest.
Erase iPhone before selling: the order beats the wipe
Germany's Verbraucherzentrale advises (9 Feb 2026) unlinking every cloud service and device activation lock before the device is reset. Plenty of guides tell you to wipe your phone before selling. Almost none give the order:
Sign out of iCloud, or pull the Google account in account settings.
Take out the SIM and memory card, as Bitkom recommends.
Then reset.
Check it boots into first-time setup.
Do it backwards and Activation Lock, or Android's Factory Reset Protection, stays on a phone that is already empty. That happens often enough that rebuy admits it (19 May 2021): when an iPhone arrives still tied to the seller's iCloud, they ask the previous owner to disconnect it. Sounds obvious. Gets forgotten constantly.
This post reflects the cited sources as of their dates. Not legal advice.
Almost everyone compares prices. Almost nobody reads the erasure promise. Both are published openly, which is the odd part. While you're checking, what a refurbished warranty covers belongs in the same round, and for the phones that stay in the drawer anyway, there is hidden raw-material value.
Frequently Asked Questions
Does a factory reset delete everything on a modern phone?
On an encrypted device, in practice yes. The BSI notes that ordinary deletion only clears index references, while erasing the keys securely is enough. Apple describes its own erase the same way.
What is the difference between a factory reset and certified erasure?
A factory reset is the function built into the phone that anyone can trigger. Certified erasure is a documented process using dedicated software. Of the four retailers compared here, only asgoodasnew names a tool: Blancco.
Should I sign out of iCloud before or after the reset?
Before. The Verbraucherzentrale advises (9 Feb 2026) unlinking all cloud services and device activation locks before resetting. Reverse that order and the lock stays active on a device that has already been wiped.
What if a refurbished iPhone still shows Activation Lock?
Only the previous Apple Account can clear it, meaning the former owner or the retailer. Another reset won't help, the lock survives it. With a commercial seller this is a complaint case.
Sources
- Bitkom asked 1,004 people aged 16 and over on 15 April 2026 bitkom.org
- BSI bsi.bund.de
- Apple's security documentation support.apple.com
- NIST SP 800-88 Rev. 1 (2014) nvlpubs.nist.gov
- 2015 research.ed.ac.uk
- supported encryption source.android.com
- asgoodasnew asgoodasnew.de
- rebuy rebuy.de
- refurbed refurbed.de
- Back Market backmarket.de
- Verbraucherzentrale advises (9 Feb 2026) verbraucherzentrale.de
- rebuy admits it rebuy.de
