About
Build. Simulate. Understand.
CircuitSimulate is a real electronics lab that lives in a browser tab. You draw a schematic, press run, and a genuine solver works out the voltages and currents — then draws them back onto the wires you built.
Why we built it
Most "circuit simulators" you find in a browser are really diagrams that light up on cue. They look convincing until you change a resistor value and nothing moves the way physics says it should. We wanted the opposite: a tool that is honest about the math, quick to open, and pleasant enough that you reach for it before wiring up a breadboard.
So the core of CircuitSimulate is a modified-nodal-analysis (MNA) engine — the same approach that powers SPICE. It assembles the system of equations for your circuit and solves it for a DC operating point, steps it through time for transient analysis, and sweeps frequency for AC analysis. There are no fake animations layered on top; the animated current you see is drawn from the current the solver actually computed.
How it is put together
The whole site is static and served as plain HTML, so pages appear the moment you ask for them. The simulator itself is a single interactive island — one focused canvas app rather than a page bloated with widgets. Heavy work happens in a Web Worker, which keeps the solver off the main thread so panning, zooming and editing stay smooth even mid-analysis.
The engine is deliberately independent of the interface. It is unit-tested on its own terms, which means the numbers can be trusted regardless of what the UI happens to be drawing. That separation is why we can promise that a reading on the multimeter is a solved result, not a prop.
Where your data lives
Nothing you build leaves your machine unless you decide it should. Projects are stored in your browser with IndexedDB, simulations run entirely client-side, and a share link encodes the circuit in the URL fragment — which never even reaches a server. No account, no tracking, no upload. Privacy here is a consequence of the architecture, not a policy bolted on afterward. The details are in our privacy policy.
Every number is solved
No scripted animations or canned results. A modified-nodal-analysis solver — the same math SPICE uses — builds the conductance matrix and solves the circuit. What you read is what the analysis returns.
Fast by construction
The site is static HTML that loads instantly. The app is a single interactive canvas island, and the solver runs in a Web Worker so the interface never stutters while a transient sweep is grinding.
Your circuits stay yours
Projects are saved locally in your browser. Nothing is uploaded, there is no account, and a share link carries the whole circuit in the URL rather than on our servers.
See it solve something.
Open a blank canvas, or start from one of the worked example circuits.