TkGate is an open source educational and reference application for digital and analog circuit design and simulation. It provides a simulation environment for designing, testing, and analyzing logic circuits. It is designed to be easy to use and understand, and to provide a highly visual and interactive experience for understanding the behavior of complex digital and analog circuits. It supports both schematic capture and SPICE-like netlist entry for circuit design, and provides a range of tools for simulating and analyzing circuit behavior. TkGate also provides an interactive debugging environment for debugging circuits, as well as a library of standard logic components and user-defined components. The application can be used to teach students the fundamentals of digital and analog circuit design and simulation, as well as to assist professional engineers in the design and verification of increasingly complex circuits.
Discontinued http://www.cburch.com/logisim/retire-note.html
Circuit Simulator
Logisim
PSIM
Hradla
CircuitVerse.org
It has many components, it does not need installation (in the browser).