Real machine physics
Every scenario simulates real equipment. Tanks fill, motors spin, valves modulate — driven by your actual ladder logic.
Free Alternative
PLC Sim — Free Browser-Based Alternative
Looking for a PLC sim? Here is a free alternative that runs in any browser — no Siemens license, no install, no Windows requirement. Three dialects, 40 auto-graded scenarios.
How it feels
Built to build intuition.
A browser tab that behaves like a real PLC bench — without the hardware budget.
Live I/O experimentation
Toggle inputs by hand to see how the PLC responds. No wiring, no hardware — just click and learn.
Certificate-backed interview prep
Pass an interview track and earn a downloadable PDF certificate. Pro users get solution walk-throughs with expert commentary on every scenario.
Live PLC sim. No install. No license key.
Context
What people usually mean by “PLC Sim”
When most engineers type “PLC Sim” into a search bar, they are often thinking of Siemens PLCSIM — the proprietary software simulator that ships with TIA Portal. PLCSIM is a solid tool: it runs actual S7-1200 and S7-1500 firmware in a virtualised environment, integrates with the TIA Portal IDE, and supports Profinet and OPC UA communications. For a Siemens-shop controls engineer on a licensed Windows workstation, it is the right choice. The catch is access friction: TIA Portal licenses start at hundreds of dollars, the installer is several gigabytes, and the whole toolchain is Windows-only. If you are a student on a Mac, a self-learner without a budget for vendor software, or an engineer who wants to sketch a logic change during a flight, that friction matters.
Our platform is a different product with similar intent: a software-only plc simulation environment you can open in any browser tab. It is not Siemens PLCSIM, it does not load Siemens project files, and it is not affiliated with Siemens AG. What it does do is run a real scan-cycle engine against IEC 61131-3, Allen-Bradley-style, and Siemens-style ladder logic and Structured Text — for free, with no install, on any operating system. Think of it as a plcsimulator for practice and learning rather than a hardware-specific commissioning tool.
Why us
Why use our PLC sim instead
Four things that make this the practical choice for learners, students, and engineers who do not want install friction.
Browser-based — no install
Open a URL. Write a rung. No TIA Portal, no Windows-only runtime, no gigabyte installer. Works on any machine with a modern browser — Chromebooks included.
Free tier — no license key
Two complete, auto-graded scenarios are free with no account and no credit card. Siemens PLCSIM requires a TIA Portal license that starts in the hundreds of dollars.
Three dialects in one editor
Switch between IEC 61131-3 Structured Text, Allen-Bradley RSLogix-style rungs, and Siemens-style networks from the toolbar. Same scenario, same physics, three ways to write the solution.
Auto-graded scenarios
Every scenario ships with hidden test cases that evaluate your logic for correct sequencing, interlock behaviour, and timing. You get a pass/fail result plus the exact failure reason — not just a blinking light.
Honest comparison
Where our PLC sim differs from Siemens PLCSIM
Siemens PLCSIM runs real S7 firmware inside a virtualised CPU. That means it accurately emulates bus timing, firmware-specific behaviour, and the exact instruction set of a physical Siemens controller. If you are commissioning a real plant with a Siemens S7-1500, PLCSIM gives you near-hardware fidelity — and that is not something we match.
We do NOT
- Run actual S7-1200 or S7-1500 firmware
- Integrate with TIA Portal
- Emulate bus communications (Profinet, Profibus, OPC UA)
- Load real Siemens project files
We DO
- Execute IEC 61131-3, AB-style, and Siemens-style ladder and ST
- Simulate scan cycle, IO table, and machine physics
- Grade your program against hidden test cases
- Run free, in any browser, on any OS
The right tool depends on what you are doing. For commissioning a real Siemens installation, use PLCSIM. For learning PLC logic, practicing for interviews, or testing control patterns without hardware, this plc sim is the faster, cheaper path.
Scenarios
Core PLC sim scenarios
Start with the free scenarios — no account needed. Each one is a full machine model with an IO list, a written objective, and a scripted test suite. The library has 40 scenarios in total.
Traffic Light
FreeFour-way signal with timer chain and all-red safety interlock phase.
Motor Start / Stop
FreeThree-wire control with seal-in, E-stop, and thermal overload interlock.
Conveyor Sort
BasicPhoto-eye sort station with part counters and reject actuator output.
Tank Fill Station
BasicLevel sensors with hysteresis control and latched high-level alarm.
PID Temperature
ProClosed-loop temperature control with tunable PID and setpoint ramp.
Batch Mixer
ProMulti-step sequencer with ingredient timing and agitator interlock.
Showing 6 of 40 scenarios. View all 40 →
FAQ
Common questions about the PLC sim.
No. Siemens PLCSIM is a Siemens AG product bundled with TIA Portal — Windows-only and license-gated. This is a separate, independent PLC sim running in any browser. It is not affiliated with Siemens AG, cannot open Siemens project files, and does not emulate S7-1200 or S7-1500 firmware. It does offer a Siemens-style dialect alongside IEC 61131-3 and Allen-Bradley.
Open the PLC Sim Free
Two scenarios, no credit card, no install — or open the Traffic Light scenario right now without an account.
PLCSIM and TIA Portal are registered trademarks of Siemens AG. This site is not affiliated with or endorsed by Siemens AG.