Schematics is described as 'com empowers engineers to design, share, and collaborate on circuit design online' and is a Circuit Simulator in the Education & Reference category. There are more than 25 alternatives to Schematics, not only websites but also apps for a variety of platforms, including Windows, Linux, Mac and Android. Most alternatives are Circuit Simulators and CAD Software. The best alternative is KiCad, which is both free and Open Source. Other great sites and apps similar to Schematics are Fritzing (Paid, Open Source), QUCS (Free, Open Source), LibrePCB (Free, Open Source) and LTspice (Free).
The Quite Universal Circuit Simulator (QUCS) is an integrated circuit simulator allowing the simulation and graphical presentation of results of large-signal, small-signal and noise behavior in circuits.
This electronic circuit simulator is highly interactive giving the feeling of playing with real components. It's very helpful for experimentation and visualization. It's a desktop version of the Circuit JS.
The gEDA project has produced and continues working on a full GPL'd suite and toolkit of Electronic Design Automation tools. These tools are used for electrical circuit design, schematic capture, simulation, prototyping, and production.
Sketch, simulate, and share your circuits, entirely in your browser -- no install required. Easy schematic capture and powerful SPICE-like, mixed-mode circuit simulation helps EE students, electronics hobbyists, and electrical engineers design faster.