You could argue that hypervisor <i>is</i> a special type of OS.<p>Compared to a &quot;traditional OS&quot;:<p>- hypervisor is much smaller, and as a result reduces security risk<p>- hypervisor is younger and has less compatibility burden, so typically carries less technical debt, can improve faster.<p>- hypervisor exposes lower-level interface, so more work is left to the app developer (or the build toolchain, which is where unikernels come in).<p>- hypervisor has no support for legacy APIs such as posix or win32. As a result almost no applications target it, which makes it a hidden piece of plumbing and makes it harder to replace the traditional OS, even when it&#x27;s redundant from a strictly technical point of view.