Free Online Electronics Simulator
Build, wire and test in your browser
A complete electronics workbench: SPICE-accurate analog parts, 19 simulated microcontrollers (Arduino, ESP32, RP2040, ATtiny85, Raspberry Pi 3), 100+ components, and live instruments — all in one canvas. Free, no install, no account.
Free & open-source · No signup required · Real SPICE + real CPU emulation
What's inside
One tool, every layer of an electronics project — from the resistor on your breadboard to the firmware on your microcontroller.
SPICE analog solver
Real ngspice via WebAssembly. 100+ device cards: passives, BJTs, MOSFETs, op-amps, regulators, diodes, optocouplers, relays.
19 microcontrollers
Arduino Uno / Nano / Mega / ATtiny85 / Leonardo / Pro Mini, Raspberry Pi Pico (W), ESP32 / ESP32-S3 / ESP32-CAM / Nano ESP32, ESP32-C3 family, CH32V003, Raspberry Pi 3B Linux.
Custom chips
Define your own ICs in C, Rust, or AssemblyScript via the Wokwi Custom Chips API — drive pins, attributes, timers, I²C and SPI from your code.
Live instruments
Multi-channel oscilloscope, voltmeter, ammeter, signal generator (sine / square / DC) — drop on any node and watch waveforms live.
48+ visual components
LEDs, RGB LEDs, 7-segment displays, 16×2 LCD, ILI9341 TFT, NeoPixel strips, servos, buzzers, ultrasonic sensors, DHT22, MPU6050, keypads.
Arduino IDE built in
Monaco code editor, multi-file workspace, Library Manager (full Arduino library index), arduino-cli compiler, Serial Monitor.
For teachers, students & tinkerers
Velxio is free under AGPLv3 — no licence cost, no per-seat pricing, no cloud account. Self-host with one Docker command for university labs.
For courses
Use the same tool from week-1 (Ohm’s law, voltage dividers) through Arduino projects and op-amp signal chains. One UI for the whole syllabus.
For labs
Self-host on a campus server. No internet dependency, no account walls — students just open the URL.
For makers
Validate your circuit and firmware before ordering parts. The scope and DMM are already on the bench.
Frequently Asked Questions
- Is Velxio a complete electronics simulator?
- Yes. Velxio combines a SPICE-accurate analog solver, 19 simulated microcontrollers (Arduino, ESP32, RP2040, ATtiny85, Raspberry Pi 3), 100+ components, an oscilloscope, voltmeter, ammeter, and signal generator — everything you need to design and validate an electronics project end-to-end.
- Can I use it like a virtual breadboard?
- Yes. Drop components on the canvas, drag wires between pins, and the simulator builds the SPICE netlist automatically. Wires snap to a grid; components rotate in 90° increments; signal-type colours mark VCC, GND, digital, and analog routes.
- Do I need to install anything?
- No. Open velxio.dev in any modern browser and start. The SPICE solver and the AVR / RP2040 emulators run locally in your browser; Xtensa and RISC-V boards (ESP32, ESP32-C3, CH32V003) plus Raspberry Pi 3 Linux run through QEMU lcgamboa, bundled in the Docker image. Compilation of Arduino sketches uses the cloud arduino-cli backend.
- Is it good for teaching electronics?
- Yes — that is one of the design goals. Free, no install, no account, no licence cost. 100+ pre-wired example circuits cover voltage dividers, RC filters, op-amp amplifiers, transistor switches, rectifiers, and complete Arduino projects. Great for university labs and self-learners.
- Is Velxio a Tinkercad / Falstad alternative?
- Yes — and a more accurate one. Velxio runs real ngspice (the engine professional EDA tools use), and unlike those tools it also runs the firmware on the microcontroller driving the circuit. Open-source under AGPLv3.
Open your virtual breadboard
Wire your first circuit in seconds — no setup, no install, no account.
Launch Electronics Simulator →