Light-weight system monitor tool/app for OSX, Conky alternatives On common UNIX-like computer operating systems there was extremely flexible/customizeable/lightweight tool for System Stats monitoring, called Conky. I'd like to find alternative system monitoring tool for operating system stats in OS X, preferable with the same set of features or more, e.g.:


OS stats monitoring (CPU usage, mem usage, network monitoring, disk usage, "top" like process stats, uname, uptime, etc);
support of compact representation in system tray (menu bar), or/end desktop-widget view;
lightweight;
highly customizable, support of user configuration (alike in conky-app: display information either as text, or using simple progress bars and graph widgets, with different fonts and colours);


What options for application/tools exist for OS X?

I searched for the other topics, and found, that answers/questions are not well organized, some of them are really specialized, lots of duplicates, etc. Let's be more specific.

Rules to structure the answer


One app per answer.
Use this format for the first two lines of your answer:


  ## [app name](link to website)
  
  ### [App Store](link to AppStore) (price)

Check for duplicates before adding new answers.
If you find a duplicate, vote it down and encourage its poster to up-vote the original entry instead (and remove the duplicate).
Include short description (preferably not marketing text) about what this system monitor does:


which OS stats (uname, uptime, CPU usage, mem usage, disk usage, "top" like process stats, and network monitoring, just to name a few);
what are configuration options, how flexible they are;
can it be shown nicely/compact in system tray (menu bar);
can it display information either as text, or using simple progress bars and graph widgets, with different fonts and colours;
provide one-two screenshots, if possible (with permanent link)
unique features;
is it lightweight or monstrous;
etc.
MenuMeters


Official website, free &amp; open-source
A fork of MenuMeters is being maintained for El Capitan+ including Mojave and Catalina: Maintained Fork Repo




Features:


CPU, memory, disk, and network monitoring tools for Mac OS X;
are a true SystemUIServer plugins (also known as Menu Extras);
Net Meter can display network throughput as arrows, bytes per second, and/or as a graph. 
minimalism: extremely lightweight and dumb simple;
size is ~1Mb;
open-source, freeware.


Official website states about exception:


  MenuMeters cannot be used on 10.11 El Capitan


But I managed to run on OS X El Capitan (10.11.3) without any problems, I will provide the link on re-compiled version, as this tool is opensource. It works like a charm for a last year, not a single issue found even after automatic system updates.

Configuration screenshot: