It is based on Debian stable (currently 10/buster), but with a much more current Linux kernel (currently 5.9 in Kali, compared to 4.19 in Debian stable and 5.10 in Debian testing). Kali Linux 2020.4 with Xfce desktop.

Is Kali Debian 8 or 9?

The Kali Linux distribution is based on Debian Testing. Therefore, most of the Kali packages are imported, as-is, from the Debian repositories. In some cases, newer packages may be imported from Debian Unstable or Debian Experimental, either to improve user experience, or to incorporate needed bug fixes.

Is Kali Linux Debian 9?

Rather than Kali basing itself off standard Debian releases (such as Debian 7, 8, 9) and going through the cyclic phases of “new, mainstream, outdated”, the Kali rolling release feeds continuously from Debian testing, ensuring a constant flow of the latest package versions.