Removing windows.old

Hi,
As above, is it safe to remove this folder. It is taking up a lot of space on c: (more than 20 gigabytes)
Moreover. why is it there?

It is there to allow you to roll back to your previous version of Windows should you have problems after updating to the latest one (say, from Anniverary Update to the Creators Update). You have 10 days after the upgrade in which you can go back, it should be automatically deleted when the 10 days are up.

If it isn't, or you want to delete it earlier this can be done safely. TenForums has a tutorial...
Delete Windows.old Folder in Windows 10

Thanx for your answer.

It will be removed automatically after 30 days or so after an upgrade.

Steve C said:

It will be removed automatically after 30 days or so after an upgrade.

That was true for versions up to 1511. From 1607 onwards it was reduced to 10 days.

Microsoft said ... "Based on our user research, we noticed most users who choose to go back to a previous version of Windows do it within the first several days," a spokesman said in an email. "As such, we changed the setting to 10 days to free storage space used by previous copies."

https://www.computerworld.com/articl...ce-period.html