A cross-plaform FOSS ncurses-based process viewer.
"It is similar to [*nix] top, but allows you to scroll vertically and
horizontally, and interact using a pointing device (mouse). You
can observe all processes running on the system, along with their
command line arguments, as well as view them in a tree format,
select multiple processes and act on them all at once.
"
—[htop's man page]
*nix folk (which will include BSD and Linux users) may well be familiar with top, a utility that allows the user to view in real time, a list of currently running processes and provide some intracrive manipulation of them (stopping processes, and adjusting their CPU priority.). Htop is a step up from this, enabling easier navigation and differing views of the process tree. Additionally there is a display of memory and CPU usage by core.
Wrutten in 2004 by Hisham Muhammad, in C, it was developed as an improvement on top, it provides a more convenient, visual, cursor-controlled interface for sending signals to processes. Muhammad stopped being the lead developer in 2019, and a development team has taken over maintenance. At the time of writing, the version is 3.3.0, released 10 January 2024, and the source is available at https://github.com/htop-dev/htop.
Most Linux distros' repositories will include htop, so installing is a breeze. It is also available in Windows Subsystem for Linux and MacOS using homebrew.
$ xclip -o | wc -w
230