The machines
An x86 PC in the tab, and 42 systems to put in it, from a 512 byte boot sector up to a gigabyte of Haiku. Every row says what booting it downloads, on top of of emulator.
The machines
Reading the shelf.
Click the screen and every key goes to the machine, Tab, Ctrl+K and the function keys included. Esc takes it back. F is fullscreen until the machine has the keyboard, and a plain letter f once it does. Speed counts the instructions the guest retired in the last second.
The emulator is v86
by Fabian Hemmer, under the Simplified BSD licence, served from this site
and never from a CDN. The images are fetched and pinned by
tools/fetch-os.mjs; each is open source or a release whose own
terms allow it to be passed on unmodified, and those terms sit under the
picture while it runs. There is no Windows here, because no version of it
was ever released for redistribution. ReactOS is on the shelf in its place.
If a shell was all you wanted, the terminal runs
one of these as text.