CircuitLab alternative (2026): A free, actively-developed browser SPICE simulator

CircuitLab is one of the original browser-based SPICE simulators, schematic-first, capable, and well-liked by the engineers who pay for it. It is also a paid product that has slowed materially in the last few years, with the most recent feature announcement on its blog dated January 2021 and a recurring set of support-forum threads about auto-renewal and cancellation, leaving the engineers, teachers, students, and hobbyists who built workflows around it searching for an actively-maintained alternative.

This guide compares CircuitLab with the alternative we build, CircuitSim, plus the other tools that come up. Where we make a claim about CircuitLab, we link to the original source so you can read it yourself and judge.

What CircuitLab still does well

The fair starting point: CircuitLab is a working product. The schematic editor is fast and precise; the SPICE engine is solid; for users already inside it, the experience of working through a textbook problem is one of the smoother ones in browser simulation. For engineers who already pay for it and do not need anything new, the answer to "should I keep paying?" is reasonably yes.

Specific strengths worth naming before any criticism lands:

• A mature schematic editor. Keyboard shortcuts, snap-to-grid, dense routing. The kind of polish that comes from a decade of small fixes.
• A solid SPICE engine. DC operating point, AC small-signal, transient, and Monte Carlo and noise analysis, both of which are present today and which CircuitSim is still building.
• A deep built-in component library. Years of accumulated standard parts with the model coverage to match.
• An Ultimate Electronics textbook by Mike Robbins, freely available, with worked examples implemented as CircuitLab circuits. A real learning resource regardless of which simulator you end up choosing.

Where CircuitLab has slowed down

Three patterns are worth knowing about before subscribing, all of them documented on CircuitLab's own properties.

Product cadence has slowed materially. The most recent CircuitLab blog post announcing a new feature is January 27, 2021. As of May 2026, that is more than five years between publicly-announced feature releases. The "New @ CircuitLab" sidebar on every page of circuitlab.com still lists those January 2021 posts as the most recent product announcements. A long-running discussion in CircuitLab's support forum captures the educator and paying-user perspective on the trajectory; the short version is that the people who relied on CircuitLab have noticed.

Annual auto-renewal is the default, and refunds are not on offer. CircuitLab's terms of service state that fees are non-refundable for partially used periods, and annual subscriptions renew automatically. Multiple users on the platform's support forum have reported renewals firing without pre-notification and slow or absent responses from the listed support email, a pattern that shows up in the cancellation-focused threads across 2023 and an older cancellation thread on the same forum. If you subscribe, plan to cancel ahead of the renewal date if you no longer want the service, and export anything you care about first.

The free tier is built to be interrupted. CircuitLab's free editor includes upgrade prompts during a session, by long-standing user reports, every ten minutes or so. The trade-off is intentional on CircuitLab's side, and they are clear they need subscription revenue to fund the product. The effect is that the free editor is difficult to evaluate the product on for any sustained session.

None of this means CircuitLab cannot work for you, and the simulator itself is solid. It means the signals that buyers of paid software pay attention to (shipping cadence, billing transparency, support responsiveness) are worth checking before committing.

What we built differently in CircuitSim

CircuitSim Our pick

CircuitSim is built as a modern web app. SPICE engine compiled to WebAssembly running in the browser; schematic editor and netlist editor side by side; standard SPICE syntax pastes in unchanged. The shipped feature set covers what an active CircuitLab user expects, and two things CircuitLab does not do at all.

Interactive simulation mode (live-tweak)

Most browser simulators (including CircuitLab) make you re-run the simulation each time you change a component value. CircuitSim has an interactive operating-point mode that updates the schematic in real time as you turn a knob on a component: the bias point, the indicator values, and the live measurements re-solve up to 120 times per second. This is the difference between "tweak, click Run, read, tweak, click Run, read" and "tweak, watch the answer move." For teaching, it is a different category of useful.

Custom interactive components

CircuitSim's component model supports user-input-driven components, sliders, switches, potentiometers, custom-built parts that respond to live input during simulation. Combined with the custom component creator (paste a .model statement, define a .subckt, or build a fully dynamic custom component with behavioural sources and parameterised macromodels), you can publish a circuit where the reader manipulates real inputs and sees the simulated response immediately. CircuitLab does not have an equivalent.

Active development, public cadence

We ship continuously. The simulator, the schematic editor, the component library, and the educator features have all moved this year and will keep moving toward a full launch in July or August 2026. There is no five-year gap between announcements; there is a real product team shipping toward a real launch date.

Share-by-URL and group collaboration

The basic flow CircuitLab has (click a link, the circuit loads in your browser, recipients do not need an account to view and simulate) works in CircuitSim. We are extending it: team collaboration tools are listed in our pricing as part of the product, and class-and-group features are actively building toward the Fall 2026 academic season.

No subscription trap during open beta

Free during open beta. No credit card, no auto-renewal, no nag screen every ten minutes, no work locked behind a paid account. A full launch is planned for July or August 2026 with paid tiers for institutions and educators; a free individual tier will continue.

Where CircuitSim is still catching up

• Monte Carlo and noise analysis. Present in CircuitLab today; in development for CircuitSim. If those are core to your workflow, CircuitLab still wins on that specific axis.
• Built-in component library breadth. CircuitLab has more years of accumulated parts. CircuitSim ships standard SPICE models for common passives, transistors, op-amps, diodes, and logic; the library is expanding monthly toward a 5,000+ target by Fall launch. If the part you need is not yet in the library, the custom component creator handles it from a .model statement.
• Open beta. Stable simulator, active development. We say this out loud rather than hide it.

Get started free at circuitsim.com →

Other tools worth considering

LTspice Desktop, Windows-first

LTspice is Analog Devices' free desktop SPICE simulator. Deep, accurate, hand-tuned over decades, and free as in beer. There is no browser version, no Chromebook build, and the macOS build is materially less capable than the Windows one. If you can install software and you are on Windows, LTspice is exceptional. If you cannot install software, it cannot help.

EasyEDA EDA + simulation

EasyEDA sits in a different category: it is a full electronic design automation suite (schematic, simulation, PCB layout, and manufacturing) built around JLCPCB's catalogue. The free tier covers schematic capture and basic simulation; for a workflow that ends in a PCB it is worth a look. As a pure SPICE simulator it is less specialised than CircuitSim or CircuitLab.

Falstad Circuit Simulator Visualisation, not SPICE

Falstad is the venerable Java-then-JavaScript circuit simulator that pre-dates most modern web SPICE. Component models are simplified, great for showing current flow and charge accumulation, not designed to capture parasitics or temperature dependence. It is not a SPICE replacement, but it is a fantastic intuition tool and free.

Multisim Live Winding down

Multisim Live is being discontinued on September 15, 2026. If you are evaluating it now, do not adopt it; if you already use it, plan a migration. Our Multisim Live alternatives guide covers the migration options.

CircuitLab vs CircuitSim, head to head

Frequently asked questions

CircuitSim is built by a small team (Britt and Sam at Elsewhere Labs) who wanted a free, actively-developed browser SPICE simulator to exist. If CircuitLab is not the right fit for you any more, that is the gap we built CircuitSim into.

CircuitLab is a trademark of CircuitLab, Inc. LTspice is a trademark of Analog Devices, Inc. EasyEDA is a trademark of EasyEDA Inc. Multisim is a trademark of National Instruments. Falstad Circuit Simulator is the work of Paul Falstad and contributors. CircuitSim® is a registered trademark of Elsewhere Labs LLC. CircuitSim is not affiliated with any of the above. All forum quotations are reproduced as posted by the original users on CircuitLab's public support forum and are linked back to the original threads. All other marks belong to their respective owners.