Circuit Simulator Guide

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

Updated May 2026 · By the CircuitSim team · 11 min read

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.

TL;DR, Quick picks

Best free CircuitLab-style alternative: CircuitSim. Browser-based, SPICE-class engine, free during open beta, actively shipping features, plus interactive simulation and interactive components CircuitLab does not have.
Best free desktop SPICE if a browser is not required: LTspice. Free, deep component library, Windows-first.
Best for EDA workflow with PCB layout attached: EasyEDA. Free tier covers schematic capture and basic simulation; PCB layout is the main draw.

A note on bias

This guide is published on CircuitSim's website. We build a direct alternative to CircuitLab, so we have a horse in this race. We have done our best to be specific and sourced about where CircuitLab is genuinely the better tool, where CircuitSim is the right step over, and where neither is what you need. Where we cite a complaint about CircuitLab, the citation links to the original (usually a post on CircuitLab's own support forum) so you can read it in full and judge for yourself.

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.

Best for

Engineers and institutions already paying for CircuitLab who do not need anything new. People who value a long-stabilised editor and are comfortable with annual auto-renewal. Anyone who needs Monte Carlo or noise analysis in a browser today and cannot wait for the same features to ship elsewhere.

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.

Best for

Anyone who wants a modern browser-based SPICE tool without a subscription, with interactive simulation and live-input components built in, from a team that ships. Students, educators preparing for Fall 2026, hobbyists, professionals doing standard analog and digital work. The migration cost from CircuitLab is low because the underlying SPICE syntax matches.

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

Capability	CircuitLab	CircuitSim	LTspice (desktop)
Runs in a browser	Yes	Yes	No
Real SPICE engine	Yes	Yes	Yes
DC, AC, transient analysis	Yes	Yes	Yes
Monte Carlo / noise analysis	Yes	In development	Yes
Interactive simulation mode (live-tweak)	No	Yes (up to 120 Hz)	No
Custom interactive components	No	Yes	No
Custom SPICE .model imports	Yes	Yes	Yes
Runs on Chromebook / iPad	Yes	Yes	No
Share a circuit by URL	Yes	Yes	No (file only)
Most recent shipped feature announcement	January 2021	Continuously	Active
Free-tier editor without interruption screens	No (every 10 min)	Yes	Yes
Annual auto-renewal	Yes, non-refundable	No (free in beta)	No (free)
Price	$24–$2,400 / year	Free (open beta)	Free

Move a CircuitLab schematic to CircuitSim in 3 steps

Reveal the CircuitLab netlist. Open the schematic in CircuitLab and run a simulation. CircuitLab's simulator pane shows the underlying SPICE netlist alongside the schematic.
Copy the netlist text and save it locally. Select and copy the full netlist including the .tran, .ac, or .dc directives at the bottom. Save it as a plain text file as a backup, keep a local copy of every circuit you care about before cancelling, because the editor locks unsaved work behind the paywall.
Paste into CircuitSim's netlist editor. Open circuitsim.com, start a new circuit, switch to the netlist editor, and paste. Standard SPICE syntax works as-is. If a part references a CircuitLab-specific subcircuit, swap it for a generic SPICE model, the custom component creator helps when needed.

Frequently asked questions

Is CircuitLab free?

No. CircuitLab is a subscription product. Pricing starts at $24 per year and ranges up to a $2,400-per-year site licence; there is a Student Edition free with a valid .edu email and a deeply-discounted Micro Plan for student use. The free tier of the editor is heavily limited, beyond a few minutes of use, an interrupting screen prompts an upgrade, and the editor locks unsaved work behind a paid account.

Is CircuitLab still being actively developed?

CircuitLab has not stated publicly that development is paused. The observable signal is that the most recent CircuitLab blog post announcing a new feature is from January 2021. As of May 2026, that is more than five years between publicly-announced feature posts. The recent activity on circuitlab.com is now mostly user-saved circuits and forum questions rather than product announcements.

Is there a free alternative to CircuitLab?

Yes. CircuitSim is a browser-based SPICE simulator that is free to use during open beta, no credit card, no install, no time limit, no interrupting upgrade prompt every ten minutes. It supports DC operating point, AC small-signal, and transient analysis, and adds two things CircuitLab does not have: an interactive simulation mode that updates the schematic in real time as you tweak component values, and custom interactive components built for live teaching demos. LTspice is also free but is a Windows desktop application, not a browser tool.

How does CircuitSim compare with CircuitLab on simulation accuracy?

Both run a SPICE-class engine in the browser. For standard analysis types (DC, AC, transient) the results are equivalent in accuracy. The differences are around the edges: CircuitLab has more years of polish on its schematic editor and a longer-accumulated component library; CircuitSim ships new features actively, has interactive simulation and interactive components that CircuitLab does not, and an open-beta price tag of zero.

Can I import my CircuitLab schematics into CircuitSim?

Direct schematic import is not available, CircuitLab uses a proprietary format. The practical migration path is to copy the SPICE netlist that CircuitLab generates and paste it into CircuitSim's netlist editor. Analysis directives translate directly; any CircuitLab-specific subcircuit can be swapped for a generic SPICE model or rebuilt with CircuitSim's custom component creator.

I cancelled my CircuitLab subscription but I still need a circuit out of it, what do I do?

If your circuits are still accessible, copy the underlying SPICE netlist out of the simulator pane and save it as a plain text file before cancelling. CircuitLab's terms state that fees are non-refundable, and the editor locks edits behind a paid subscription, so the safest pattern is to export everything you care about first, then cancel. If you have already lost access, recreate the schematic from a screenshot or printed diagram inside CircuitSim, which is free during open beta.

What does CircuitLab do better than CircuitSim today?

CircuitLab has more years of polish on its schematic editor, a deeper accumulated component library, and an established institutional licensing story. The SPICE engine is mature and Monte Carlo and noise analysis are present today, those are still in development in CircuitSim. If a CircuitLab feature you rely on is not yet in CircuitSim, email us, knowing what blocks a migration helps us prioritise.

What should I know about CircuitLab's billing before subscribing?

CircuitLab's terms state that fees are non-refundable for partially used periods, and annual subscriptions auto-renew. Users on CircuitLab's own support forum have reported renewals firing without pre-notification and slow responses on the listed support email. If you subscribe, plan to cancel well ahead of the renewal date if you no longer want the service, and export any circuits you care about before cancelling.

Is CircuitSim really free, or is there a paid tier coming?

CircuitSim is free during open beta with no credit card and no time limit. A full launch is planned for July or August 2026 with paid tiers for institutions and educators after launch; a free individual tier will continue. We will give plenty of notice before anything changes for existing users.

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.

Start simulating free at circuitsim.com →

Sources

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.