This is recorded from the working simulator—not a conceptual mockup. See the editor, live I/O and industrial scenario respond together before you create an account.
Free PLC Simulator — program a PLC in your browser
What the footage proves
Program the real simulator
Write ladder or structured text, run the scan, toggle live I/O and see the machine state respond.
Learn inside industrial scenarios
Practice motors, tanks, conveyors, alarms and interlocks instead of watching a decorative animation.
Get a guided next step
Use checks, explanations and structured learning paths to move from a first rung to job-relevant control work.
No install. No card. Start with a working circuit.
This is our PLC simulator — equivalent to what most “PLC emulator” searches actually want.
An online PLC emulator alternative that runs entirely in the browser — no Windows, no install, no license key.
The honest distinction
PLC Emulator vs Simulator — What's the Difference?
A PLC emulator runs the actual firmware of a specific controller in a virtual machine. Rockwell's Studio 5000 Logix Emulate, for example, executes real ControlLogix firmware on your Windows PC — cycle-accurate scan times, vendor-identical instruction behaviour, hardware-specific diagnostic codes. Siemens PLCSIM does the same for S7 and S7-1500 firmware inside TIA Portal. These are genuine firmware emulators: the same binary that runs on the physical rack runs inside the VM.
A PLC simulator replicates the behaviour of a PLC without running vendor firmware. It parses your ladder logic or Structured Text into an intermediate representation, schedules a scan cycle, evaluates every rung against an IO table, and drives a software model of the machine. The timing is not cycle-accurate to specific hardware. The instruction set is modelled, not firmware-identical. But for the vast majority of use cases — learning ladder logic, testing control sequences offline, teaching PLC programming to a class, preparing for a technical interview — a simulator gives you everything you need without the Windows dependency, the multi-gigabyte install, or the paid vendor license.
Both a real PLC and a simulator run the same loop: read inputs → execute logic → update outputs → repeat. The simulator runs it in your browser instead of on firmware.
Whether it runs on a real ControlLogix rack, inside Logix Emulate, or in our browser-based simulator, the scan cycle is identical in shape: read every physical and internal input into an image table, solve each rung top-to-bottom and left-to-right, write the results to the output table, then loop. What a true emulator adds is firmware-exact timing for that loop. What a learning simulator gives you is the same logical behaviour with instant feedback — which is precisely what you want when the goal is to understand the logic, not to certify a scan time.
The architecture a PLC emulator reproduces: CPU, input/output modules, and the IO image table. Our simulator models the same structure in software.A single ladder rung: input contacts in series and parallel feeding an output coil. The simulator solves each rung left to right, exactly as a real PLC scan does.
Our product is a simulator. It runs your ladder logic through a scan cycle, drives a physics model of a real machine, and grades your output against a scripted test harness. It supports IEC 61131-3, Allen-Bradley, and Siemens dialects in the same editor, free, in any browser. For the “I need to test my PLC code without hardware” use case — which is what most people searching for a free PLC emulator online actually want — this is the right tool. We will tell you clearly below when it is not.
Be honest about it
When You Need a True PLC Emulator
There are use cases where only a firmware emulator will do. If any of the following apply to your project, use the vendor tool.
⚠Production code validation for high-reliability systems. Safety-rated or regulatory-certified code must be validated against the exact firmware that runs on the production rack.
⚠Cycle-time tuning against specific hardware. If your application depends on a specific scan rate or instruction execution time, you need firmware running in a VM, not a browser-simulated scan.
⚠Firmware-specific bug reproduction. Hardware-specific edge cases in instruction handling require the actual firmware to reproduce reliably.
⚠Vendor-approved commissioning dry-runs. Some project contracts require a PLCSIM or Logix Emulate acceptance test before site commissioning.
Vendor firmware emulators for these use cases:
Rockwell Studio 5000 Logix Emulate — runs real ControlLogix firmware, Windows-only, approximately $1,500 license. [ESTIMATE — verify current Rockwell pricing]
Siemens PLCSIM — bundled with TIA Portal, Windows-only, TIA Portal license approximately $1,500+. [ESTIMATE — verify current Siemens pricing]
If your goal is any of the following, a simulator — ours in particular — is faster, cheaper, and more accessible than a firmware emulator.
✓Learning ladder logic or Structured Text from scratch.
✓Students practicing machine control scenarios outside the lab — no admin-locked installs, no per-seat licenses.
✓Interview preparation — testing your logic against graded scenarios before a technical assessment.
✓Verifying logic changes offline before a commissioning window, when cycle-accurate timing is not a requirement.
✓Building a portfolio of working PLC programs to show a hiring manager.
✓Teaching PLC programming to groups — browser-based means Chromebook-friendly, no IT involvement.
✓Exploring how industrial control patterns work (interlocks, sequencers, PID loops) without physical hardware.
What you get
Features of Our PLC Simulator (the Emulator Alternative)
Six reasons this simulator covers the same ground as a PLC emulator for learning, teaching, and offline logic development.
Three dialects in one editor
IEC 61131-3 Structured Text, Allen-Bradley RSLogix-style, and Siemens TIA Portal-style. Switch dialect on any scenario without losing your code.
170 published scenarios
Every scenario ships with a scripted test harness that evaluates correct sequencing, interlock behavior, and timing windows — then returns pass/fail with a specific failure reason.
Browser-based — any OS
No install, no Windows dependency, no vendor license key. Works on Chrome, Firefox, Safari, Edge — including Chromebooks and macOS.
Free tier, no credit card
One guided first program needs no account. A free account has 32 source-tagged practice records, no credit card and no trial clock; visible access can vary by entitlement and rollout.
Hidden test cases grade your logic
You see the objective, not the test suite. The grader evaluates your program against scenarios it was not written for — the same pressure as a real interview coding challenge.
Structured Text + ladder editor
Monaco-based editor with syntax highlighting, VAR block support, and the full IEC 61131-3 instruction set: XIC, XIO, OTE, TON, CTU, R_TRIG, PID, and more.
One editor, three dialects — IEC 61131-3, Allen-Bradley, and Siemens
A vendor firmware emulator locks you to one ecosystem — Logix Emulate runs RSLogix/Studio 5000 code, PLCSIM runs TIA Portal code. This simulator instead normalises three dialects into one execution model, so you can write the same control problem in standards-based IEC 61131-3 Structured Text, in Allen-Bradley RSLogix-style ladder, or in Siemens TIA-style ladder, and run all three against the identical graded scenario. That makes it a practical way to learn the patterns that transfer across every vendor, not just one.
The IEC 61131-3 language family. This simulator runs Ladder and Structured Text, the two dialects you meet most often across Allen-Bradley and Siemens.Write standards-based Structured Text in the Monaco editor — VAR blocks, IF/THEN, and the full instruction set — and run it on the same scan cycle as ladder.Inputs and outputs are tracked in a live IO table you can watch update every scan, exactly as you would on real hardware.
Comparison
Comparing PLC Emulators and Simulators
An honest side-by-side. Each product listed here does something useful. The differences are in type, cost, and access friction.
Product
Type
License
Install
Scenarios
Studio 5000 Logix Emulate
Firmware emulator
~$1,500 [ESTIMATE]
Windows
Custom
Siemens PLCSIM
Firmware emulator
~$1,500+ with TIA [ESTIMATE]
Windows
Custom
This platform
Simulator
Free tier available
None (browser)
40 pre-built
PLC-Fiddle
Simulator
Free
None (browser)
Minimal
OpenPLC
Simulator / runtime
Free
Linux / Windows
User-built
Pricing estimates are approximate and subject to change. Verify current licensing costs directly with Rockwell Automation and Siemens. This site is not affiliated with or endorsed by any vendor listed in this table.
No download
How to Start the PLC Emulator in Under a Minute
A vendor firmware emulator like Logix Emulate or PLCSIM is a multi-gigabyte Windows install behind a license server. This browser-based simulator skips all of that — there is nothing to download, no Windows requirement, and no key to enter.
2.Write your control logic in the editor — ladder rungs or IEC 61131-3 Structured Text — in your chosen dialect.
3.Press Run. The scan cycle starts, the IO table updates live, and the simulated machine reacts on screen.
4.The hidden test harness grades your program and tells you exactly which case passed or failed — iterate until it is green.
The first program most people run: three-wire motor control with seal-in. Build it in ladder, press Run, and watch the contactor latch in the simulated IO table.
Once the basics click, most scenarios add a timing element. The emulator runs the standard IEC 61131-3 timers — TON (on-delay), TOF (off-delay), and TP (pulse) — on the same scan, so a timer's accumulated value advances every cycle exactly as it would on a real controller.
On-delay (TON), off-delay (TOF), and pulse (TP) timers all run on the simulated scan — accurate relative to the scan, though not cycle-accurate to a specific hardware clock.
Start here
Core Scenarios to Try
Six of the 170 published scenarios — covering machine types that appear most often in PLC programmer assessments and on the shop floor. The guided first program opens without an account; catalog progress uses a free account.
Common questions about PLC emulators and simulators.
It is a simulator, not a firmware emulator. A true PLC emulator — Rockwell Studio 5000 Logix Emulate or Siemens PLCSIM — runs actual controller firmware in a virtual machine, cycle-accurate and vendor-identical. Our platform simulates the logic layer: your ladder logic executes on a scan cycle, drives a physics model, and returns auto-graded results. For learning, teaching, and most logic-testing use cases, that is exactly what you need.
PLC emulator for browser-based logic practice: test checklist
Direct answer
The reader can match emulator fidelity to the decision being tested, run a bounded logic-and-I/O case and identify what still requires the official vendor environment or hardware.
Written for pLC learners and controls professionals deciding whether they need an educational browser emulator, a vendor controller emulator or real target hardware.
System map / 02
NODE 01observable
01
Scenario setup
The exact decision, controller family, language, instruction set, I/O behavior, timing tolerance and target evidence required.
NODE 02observable
02
I/O and state map
Input stimulus through scan evaluation, internal state and output command to observable simulated feedback.
NODE 03observable
03
Normal run
A start-stop, timer, permissive and fault-recovery case with named expected results.
NODE 04observable
04
Boundary run
First scan, timer boundary, simultaneous inputs, retained state, power return and unsupported instruction behavior.
NODE 05observable
05
Injected fault
A parser, scan, address, state, I/O mapping or expectation mismatch located from the first disagreeing signal.
NODE 06observable
06
Target check
The logic transferred to the official emulator or target controller and rerun under the applicable acceptance procedure.
Rockwell Automation, Studio 5000, and Logix Emulate are trademarks of Rockwell Automation, Inc. Siemens and PLCSIM are trademarks of Siemens AG. Beckhoff and TwinCAT are trademarks of Beckhoff Automation GmbH & Co. KG. This site is not affiliated with or endorsed by any of these companies.