Debian is a collaboratively developed free operating system. Debian GNU / Linux is based on the basic system tools of the GNU project as well as the Linux kernel. The current version is Debian 9 “Stretch”. Debian includes a wide range of application programs and tools. Currently, there are over 51,000 program packages.

Debian Linux is the most widely used Linux distribution for web servers, ranging from enterprise hosting to retail hosts (see Siteground review on security).

According to an online survey conducted by Heise online in February 2009, Debian Linux is the most widely used free server operating system in German companies with 47 percent (multiple choice possible). Among free desktop operating systems, Debian Linux occupies second place behind Ubuntu (60.8%), which is also derived from Debian – closely followed by openSUSE (28.8%, as of February 2009).