Like Qucs, but in your browser and built for digital logic
Qucs-S ("Qucs with SPICE") is a free, open-source (GPL-2.0) circuit simulation program with a Qt-based graphical interface for several simulation engines: Ngspice (recommended), Xyce, SpiceOpus and the non-SPICE Qucsator. It is based on the original Qucs code, its latest stable release is 26.1.1, and it has packages for Linux, Windows and macOS (through Homebrew). If that is what brought you here, digiwleea is a free, in-browser alternative with a different angle: you build a computer from the transistor up.
What Qucs-S is good at
It puts several real simulation engines behind one friendly schematic editor, it is actively developed with regular releases, and it is free and open to contributions. If you want SPICE-level analysis of real circuits without paying for a commercial tool, it is a strong choice. (digiwleea is an independent project, not affiliated with Qucs-S.)
How digiwleea is different
digiwleea is not a SPICE front end: it treats transistors as switches, the level you need to understand digital logic and computers. It runs in any browser with nothing to install, and its course goes from CMOS gates through adders, latches, registers and RAM to an 8-bit CPU that you program in assembly, with theory lessons and an AI tutor (Wleea). Qucs-S is the better pick for analog circuit simulation; digiwleea is the better pick for learning how logic and processors work.
| Qucs-S | digiwleea | |
|---|---|---|
| Simulation | SPICE engines (Ngspice, Xyce, SpiceOpus) and Qucsator | Switch-level digital logic |
| Runs on | Linux, Windows, macOS (desktop install) | Any modern browser, nothing to install |
| Price / license | Free, open source (GPL-2.0) | Free lab and Act I; Premium for the full course |
| Guided course to a CPU | No (a simulator) | Yes, 40+ levels |
No sign-up is needed to start: open the lab and place your first transistor, or read the free theory course. The account (and the AI tutor) are optional.
See for yourself: build a logic gate from transistors in the simulator, then follow the path from sand to an 8-bit CPU.
Open the digiwleea lab →Frequently asked
Is digiwleea a good Qucs-S alternative?
Yes, if you want to understand digital logic from the ground up. digiwleea is a free, in-browser simulator with a guided 40+ level course where you build every gate from CMOS transistors and work up to a real 8-bit CPU, with an AI tutor to help.
Is digiwleea free?
The sandbox lab and the first act of the course are free and need no sign-up. An optional account adds the AI tutor and cross-device sync; the full course and expanded AI tutoring are included in the monthly or annual Premium subscription.
Do I need to install anything?
No. digiwleea runs entirely in your browser, on desktop or mobile, and works offline once loaded.