Is formatting twice 100% safe?

So the following:

I'm selling a notebook and therefore naturally want to erase the hard drive completely. Since I once heard that you can restore the data despite formatting, I thought it to myself: I format, reinstall the operating system and then format again. Then the first one is overwritten and there's no longer any access to the data, right?

I would be interested if I'm right with that.

There's the "full formatting", which takes longer and actually initializes the entire volume and not just the administrative structures. That is enough once. Data can still be reconstructed with a quick format, but repeated execution does not help either. Unless you copy so much nonsense data onto it after the first time that the disk is full to the brim, then the data will of course be overwritten.

In general, it is not necessary to overwrite the hard disk several times and to be unable to restore it to its original state.

Do you have a 2 TB disk and an OS of 0.5 TB. If you had the HDD full before, only the 0.5 TB was overwritten after the OS was loaded again, but not the 1.5 TB of the remaining data.

Therefore, you can save yourself this trouble. There are special erasing and formatting programs that write repeatedly about everything that is to be removed.

Is formatting twice 100% safe?

Double or triple (single) formatting is not enough. Simple formatting only deletes the structures, which can, however, be restored relatively easily.

My tip: Read the linked recommendation from the Federal Office for Information Security (BMI for short) and the article from the Ct carefully and follow the steps mentioned there.

https://www.bsi-fuer-buerger.de/BSIFB/DE/Empfehlungen/RichtigLoeschen/richtigloeschen_node.html
https://www.heise.de/...91831.html

Software / utilities:

https://eraser.heidi.ie/
http://www.ultimatebootcd.com/
https://www.heise.de/...dban-54943

Small addendum, because I only noticed it now: It's not called BMI, but BSI!

Federal Ministry of Illusion. Actually right.

It is even better to zero the hard disk. Preferably several times. There's also the Darik's Boot and Nuke tool: https://sourceforge.net/...ects/dban/

After the download, write the ISO to an empty formatted USB stick with Rufus https://rufus.ie/. Then boot the stick and follow the instructions of the wizard. The hard disk is overwritten with zeros.

Zeroing a hard drive is always best. This makes it extremely difficult to restore data.

The Windows 10 license is not lost because the key is permanently integrated in the BIOS and is automatically applied again when Windows 10 is reinstalled and is automatically activated.

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