PLC Simulator
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CODESYS vs a Browser PLC Simulator: Which Fits?

Compare CODESYS with a browser PLC simulator by runtime, hardware targets, IEC languages, graded practice, installation and learning workflow.

PLC Simulation Software8 min read

Codesys vs our simulator — honest comparison

Codesys is a serious piece of software. It's the runtime embedded inside PLCs from WAGO, Beckhoff, IFM, Eaton, ABB's MicroBrowser, and dozens of smaller OEMs — if you buy a non-Rockwell, non-Siemens PLC in 2026, chances are good it's running Codesys underneath. The Codesys Development System is the free desktop IDE that programs all those controllers.

Our simulator is a browser-based curriculum platform with 140 published scenario records, nine learning dialects, and built-in interview prep. Different product, different user, different use case. This post explains the difference honestly and suggests a sequence that uses both.

What Codesys actually is

Three components:

  1. Codesys Development System — the free Windows IDE. Full IEC 61131-3 support across six languages (LD, FBD, ST, SFC, IL, CFC). Mature, powerful, occasionally baroque.
  2. Codesys Control Runtime — the soft PLC that executes your code. Free for development use; paid licence per-target in production. Runs on Linux, Windows CE, RT variants, and many embedded platforms.
  3. Vendor-specific plug-ins — each vendor that embeds Codesys adds its own libraries and target support in the IDE. WAGO, Beckhoff, etc.

The Development System is free. Buying a Beckhoff PC-based PLC means you're already paying for the runtime licence bundled with the hardware.

What our simulator is

  • Browser-based PLC learning platform
  • 140 published scenario records with automated test cases; visible access varies by plan and rollout
  • 55 learning modules + 12 quizzes + 6 interview tracks
  • Nine learning dialects, including IEC 61131-3, Allen-Bradley-style, Siemens, Mitsubishi, Omron, KEYENCE, Schneider, Delta and Instruction List
  • USD 0 free tier (27 source-tagged practice records; visible access can vary), USD 99/year Basic, USD 249/year Pro
  • No install, any OS

Curriculum-led where Codesys is tool-led.

Head-to-head

Codesys vs our simulator

Reference tableSwipe
DimensionCodesysOur simulator
PlatformWindows desktopAny browser
InstallYes, 2–4 GBNo
IEC 61131-3All 6 languagesLD + ST (covers 95% of industry use)
DialectsIEC + Codesys extensionsIEC + A-B + Siemens + Delta
Machine physicsNone40 built-in scenarios
Graded assessmentsNoneAuto-graded per scenario
Interview prepNone6 tracks with certificates
Deploys to hardwareYes (Codesys-based only)No
CostFree dev; paid runtimeUSD 99–249/year

The tools are solving different problems. Codesys is the tool a working engineer uses to program real hardware. Our simulator is the curriculum that teaches someone how to be that engineer.

When Codesys is the right answer

When Codesys is the right answer

  • Your target job runs Codesys-based hardware. WAGO PFC, Beckhoff CX, IFM ecomat mobile, Eaton XC — all Codesys underneath. Learn Codesys for those.
  • You need SFC or CFC. Our simulator covers LAD and ST, not SFC or CFC. If your work is recipe-driven (brewery, pharma) or motion-heavy (CNC), Codesys supports both natively.
  • You're an experienced programmer who doesn't need curriculum. Codesys is powerful but unguided. Fine if you already think in scan cycles.
  • You want the most widely-embedded runtime to understand. Knowing Codesys deeply pays off across many vendor ecosystems.
  • You have a Windows machine and don't mind the install.

When our simulator is the right answer

When our simulator is the right answer

  • You're learning PLCs from scratch. You need curriculum, graded tests, and solutions to compare against. Codesys supplies none of that.
  • You need to read code across vendors. Four dialects in one UI beats four separate tools.
  • You're on a Mac, Chromebook, or iPad. Codesys refuses; we run.
  • Interview prep matters. The six tracks with downloadable certificates is a specific product feature nobody else offers.
  • You don't yet know whether you'll stick with PLCs. Free tier + no install is the right on-ramp.

The hybrid sequence

Most serious learners end up using both:

  1. Weeks 1–8: Our simulator. Learn fundamentals, write 20 scenarios, get your first two interview-track certificates.
  2. Weeks 9–10: Download Codesys Development System. Port a few of your scenario solutions into Codesys. Notice what's identical (the logic) and what's specific (the IDE chrome, the library catalogue, the device tree).
  3. Week 11+: If your target job is Codesys-based, work in Codesys. If it's Rockwell or Siemens, use their tools instead. Either way, keep our simulator for multi-dialect fluency and interview prep.

This sequence works because it separates learning from tooling. Most people try to learn from a tool and burn out on install friction before they've written a rung.

Common confusion

  • "Is Codesys a PLC?" No. Codesys is the software (IDE + runtime). A PLC is hardware. Codesys runs on many vendors' PLCs.
  • "Is Codesys a simulator?" It includes a soft PLC for testing, which simulates execution. It does not include machine physics or learning scenarios.
  • "Is Codesys better than Rockwell or Siemens?" Different market. Codesys-based PLCs are common in European process, building automation, and OEM machinery. Rockwell dominates North American manufacturing. Siemens dominates European automotive. Learn whichever your target requires.

FAQ

Is Codesys free?

Codesys Development System (the IDE) is free. The runtime is free for development; commercial runtime deployment is paid via your PLC manufacturer.

Is Codesys good for beginners?

For experienced programmers, yes. For complete PLC beginners without curriculum support, it's tool-heavy without guidance. Pair it with a learning resource.

What's the best Codesys tutorial?

Codesys publishes an official "Getting Started" PDF. RealPars YouTube channel has solid Codesys-specific videos. Our 12-week PLC course builds the fundamentals that make Codesys easier.

Can I learn Codesys in a browser?

Not natively. Codesys is a desktop product. For browser-only practice, our simulator covers the same IEC 61131-3 semantics with dialect toggles.

Which PLCs use Codesys?

WAGO PFC100/200, Beckhoff CX-series, IFM ecomat, Eaton XC-series, ABB AC500 (subset), and many smaller vendors. Check your target's documentation.

Where to start

  1. Complete beginner: sign up free and finish 2 scenarios. Then read this post again.
  2. Experienced programmer: download Codesys Development System directly. Work through the official Getting Started guide.
  3. Career-focused learner: use our simulator for curriculum (Weeks 1–10), then add Codesys in Week 11 if your target job requires it.

Two tools, two problems, one sequence. Pick the right one for where you are right now.

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CODESYS versus a browser PLC simulator: implementation, evidence and troubleshooting

Direct answer

CODESYS versus a browser PLC simulator becomes useful when it connects whether the goal is guided learning, iec project development, target deployment, visualization or device integration with ide, runtime, target packages, iec languages, libraries, machine model, grading and platform requirements, then proves one equivalent iec sequence tested against observable acceptance criteria under normal, boundary, fault and recovery conditions. The objective is a repeatable engineering or learning result, not merely activity inside a page or tool.

This guide is written for pLC learners and engineering teams deciding between a target-capable IEC development system and curriculum-led browser practice. The intended result is specific: the evaluator can choose by target runtime, supported language, device integration, learning feedback, machine model, operating system and deployment requirement.

System map / 02

Six concepts that control the result

Treat these as connected checkpoints. Each checkpoint has an expected state, an observable state and a boundary to the next part of the system. That structure prevents a software indication from being mistaken for physical proof.

NODE 01observable

Define the operating contract

whether the goal is guided learning, IEC project development, target deployment, visualization or device integration. For CODESYS and guided browser PLC simulation, record the initial condition, actor, requested change, observable result and stopping condition before selecting a tool or implementation.

NODE 02observable

Map the evidence path

IDE, runtime, target packages, IEC languages, libraries, machine model, grading and platform requirements. Separate request, internal state, output or service, physical or user-visible result and independent feedback so each boundary can be inspected.

NODE 03observable

Prove normal operation

one equivalent IEC sequence tested against observable acceptance criteria. Run more than one cycle from a known state and retain the values, timings or artifacts that demonstrate repeatability.

NODE 04observable

Exercise a boundary case

target licences, device descriptions, libraries, task configuration, operating system and commissioning access. Choose minimum, maximum, simultaneous, delayed or restart conditions that reveal assumptions hidden by the happy path.

NODE 05observable

Diagnose a controlled fault

a syntax, compile, runtime, mapping or target mismatch found through the same case. Preserve the first symptom, divide the system at a measurable boundary and change one condition only after predicting the result.

NODE 06observable

Transfer and hand over

the learned behavior ported, compiled and accepted in the required target toolchain. Restore normal state, remove temporary changes, repeat affected checks and document which claims remain limited to the learning environment.

Procedure / 03

A six-step practice and commissioning workflow

Run the steps in order the first time. Later, the same structure becomes a diagnostic loop: define the expected condition, observe the boundary, interpret the difference and choose one proving action.

  1. 01

    Write the acceptance case

    Convert whether the goal is guided learning, iec project development, target deployment, visualization or device integration into initial conditions, one stimulus and observable pass criteria.

    Evidence: Another person can repeat the case without guessing the intended result.

    Avoid: Using page completion or an animation as the acceptance criterion.

  2. 02

    Build the map

    Document ide, runtime, target packages, iec languages, libraries, machine model, grading and platform requirements and name who owns each state or decision.

    Evidence: Every request and result has a source, destination and useful inspection point.

    Avoid: Using the same value as command, status and independent feedback.

  3. 03

    Run the baseline

    Apply one equivalent iec sequence tested against observable acceptance criteria from a clean start and record the expected evidence.

    Evidence: Repeated runs produce the same bounded result.

    Avoid: Changing several parameters before a baseline exists.

  4. 04

    Challenge assumptions

    Test target licences, device descriptions, libraries, task configuration, operating system and commissioning access without changing the acceptance contract.

    Evidence: Limits, timing and restart behavior reach defined states.

    Avoid: Testing only one ideal sequence.

  5. 05

    Isolate one failure

    Introduce or analyse a syntax, compile, runtime, mapping or target mismatch found through the same case and locate the first disagreement.

    Evidence: The proving action distinguishes the leading hypotheses.

    Avoid: Resetting, forcing or replacing before evidence is retained.

  6. 06

    Close the evidence loop

    Complete the learned behavior ported, compiled and accepted in the required target toolchain and repeat the affected regression cases.

    Evidence: An evaluation is complete when the same representative job is tested in each candidate and differences are recorded as evidence rather than inferred from feature labels.

    Avoid: Treating an acknowledged message or one successful rerun as handover.

Diagnostic matrix / 04

Symptoms, proving points and next actions

The table is a reasoning aid, not a parts-replacement chart. Preserve the initial symptom, inspect the named boundary and use the interpretation to choose the next controlled test. Site safety procedures and equipment manuals remain authoritative.

Diagnostic symptoms, inspection points, interpretations and next actions for CODESYS versus a browser PLC simulator: implementation, evidence and troubleshooting
Observed symptomInspectInterpretationNext proving action
The expected result is unclearRequirement, initial state, actor, stimulus, units and pass conditionThe evaluator, instructor and technical buyer may be solving different versions of the task.Rewrite one observable acceptance case before continuing.
Internal state changes but the outcome does notRequest, final owner, output or service boundary and independent feedbackA software or interface indication proves intent at one layer, not the complete outcome.Trace the first boundary after the changing state.
Normal case passes but an edge case failsLimits, timing, simultaneous events, reset and restart assumptionsThe implementation contains a hidden assumption exposed by the changed condition.Add the failed boundary as a permanent regression case.
The failure disappears after resetOriginal symptom, histories, diagnostics, timestamps and active causeReset changed evidence or state without proving the initiating cause.Reproduce under a controlled condition and preserve pre/post-event data.
Simulator and target disagreeModel boundary, software version, task timing, I/O behavior, data types and configurationA learning model and the intended target do not share one of the recorded assumptions.Reduce the case and verify against current target documentation.
The result cannot be explainedPrediction, observation, proving action, alternative hypotheses and limitationsActivity occurred but the evidence is not yet transferable or reviewable.Have the learner defend the signal path and repeat a changed case.

Product evidence / 05

What the browser practice can actually demonstrate

The public product surface exposes runnable examples, capability boundaries, pricing context and test-harness behavior that can be checked before a purchasing decision.

Where simulation stops

The browser simulator is not a CODESYS runtime or project-file replacement; CODESYS capabilities depend on release, target package and controller vendor.

Commissioning notebook / 06

Six cases that turn the concepts into evidence

Use these as written briefs rather than click-through instructions. For every case, state the expected condition before acting, retain the first useful observation and explain why the final result proves the requirement. A different program or component choice can still be correct when it produces the same bounded behavior and evidence.

Case 01

predict → observe → prove

Prove define the operating contract

Engineering context. whether the goal is guided learning, IEC project development, target deployment, visualization or device integration. For CODESYS and guided browser PLC simulation, record the initial condition, actor, requested change, observable result and stopping condition before selecting a tool or implementation. Begin with a written normal condition and identify which request, state, physical result or communication value will provide independent confirmation. Do not begin by changing the configuration; the initial state is part of the evidence and should remain reproducible.

Controlled setup. Use the “Write the acceptance case” stage of the workflow: convert whether the goal is guided learning, iec project development, target deployment, visualization or device integration into initial conditions, one stimulus and observable pass criteria. The acceptance record should show this result: another person can repeat the case without guessing the intended result. Record initial conditions, the exact stimulus and the observation point so another learner can repeat the case without relying on your memory.

Fault challenge. Introduce or analyse “The expected result is unclear” as one bounded deviation. Inspect requirement, initial state, actor, stimulus, units and pass condition The working interpretation is that the evaluator, instructor and technical buyer may be solving different versions of the task. The next proving action is to rewrite one observable acceptance case before continuing. Change only one condition before observing the result, and preserve timestamps or measurements where timing matters.

Review and recovery. The most common trap here is using page completion or an animation as the acceptance criterion. After restoring the cause, repeat the normal case and at least one stop, timeout, disconnect or restart boundary relevant to this topic. Remove temporary forces and bypasses, return the model to a known state and retain the evidence that both operation and recovery are deliberate.

Explain it aloud: What should I learn first about CODESYS and guided browser PLC simulation? A defensible short answer is: Start with the operating contract and evidence path: whether the goal is guided learning, iec project development, target deployment, visualization or device integration, followed by ide, runtime, target packages, iec languages, libraries, machine model, grading and platform requirements. Add advanced features only after the baseline is predictable.

Case 02

predict → observe → prove

Prove map the evidence path

Engineering context. IDE, runtime, target packages, IEC languages, libraries, machine model, grading and platform requirements. Separate request, internal state, output or service, physical or user-visible result and independent feedback so each boundary can be inspected. Begin with a written normal condition and identify which request, state, physical result or communication value will provide independent confirmation. Do not begin by changing the configuration; the initial state is part of the evidence and should remain reproducible.

Controlled setup. Use the “Build the map” stage of the workflow: document ide, runtime, target packages, iec languages, libraries, machine model, grading and platform requirements and name who owns each state or decision. The acceptance record should show this result: every request and result has a source, destination and useful inspection point. Record initial conditions, the exact stimulus and the observation point so another learner can repeat the case without relying on your memory.

Fault challenge. Introduce or analyse “Internal state changes but the outcome does not” as one bounded deviation. Inspect request, final owner, output or service boundary and independent feedback The working interpretation is that a software or interface indication proves intent at one layer, not the complete outcome. The next proving action is to trace the first boundary after the changing state. Change only one condition before observing the result, and preserve timestamps or measurements where timing matters.

Review and recovery. The most common trap here is using the same value as command, status and independent feedback. After restoring the cause, repeat the normal case and at least one stop, timeout, disconnect or restart boundary relevant to this topic. Remove temporary forces and bypasses, return the model to a known state and retain the evidence that both operation and recovery are deliberate.

Explain it aloud: How do I practise CODESYS and guided browser PLC simulation effectively? A defensible short answer is: Use short cases with known initial conditions, a written prediction, one action and an observable result. Then alter a boundary or fault and explain why the evidence changed.

Case 03

predict → observe → prove

Prove prove normal operation

Engineering context. one equivalent IEC sequence tested against observable acceptance criteria. Run more than one cycle from a known state and retain the values, timings or artifacts that demonstrate repeatability. Begin with a written normal condition and identify which request, state, physical result or communication value will provide independent confirmation. Do not begin by changing the configuration; the initial state is part of the evidence and should remain reproducible.

Controlled setup. Use the “Run the baseline” stage of the workflow: apply one equivalent iec sequence tested against observable acceptance criteria from a clean start and record the expected evidence. The acceptance record should show this result: repeated runs produce the same bounded result. Record initial conditions, the exact stimulus and the observation point so another learner can repeat the case without relying on your memory.

Fault challenge. Introduce or analyse “Normal case passes but an edge case fails” as one bounded deviation. Inspect limits, timing, simultaneous events, reset and restart assumptions The working interpretation is that the implementation contains a hidden assumption exposed by the changed condition. The next proving action is to add the failed boundary as a permanent regression case. Change only one condition before observing the result, and preserve timestamps or measurements where timing matters.

Review and recovery. The most common trap here is changing several parameters before a baseline exists. After restoring the cause, repeat the normal case and at least one stop, timeout, disconnect or restart boundary relevant to this topic. Remove temporary forces and bypasses, return the model to a known state and retain the evidence that both operation and recovery are deliberate.

Explain it aloud: What counts as proof of competence? A defensible short answer is: A repeatable artifact or system result plus an explanation of the signal path is stronger than time spent, screenshots or a copied answer. Physical competence requires separate supervised evidence.

Case 04

predict → observe → prove

Prove exercise a boundary case

Engineering context. target licences, device descriptions, libraries, task configuration, operating system and commissioning access. Choose minimum, maximum, simultaneous, delayed or restart conditions that reveal assumptions hidden by the happy path. Begin with a written normal condition and identify which request, state, physical result or communication value will provide independent confirmation. Do not begin by changing the configuration; the initial state is part of the evidence and should remain reproducible.

Controlled setup. Use the “Challenge assumptions” stage of the workflow: test target licences, device descriptions, libraries, task configuration, operating system and commissioning access without changing the acceptance contract. The acceptance record should show this result: limits, timing and restart behavior reach defined states. Record initial conditions, the exact stimulus and the observation point so another learner can repeat the case without relying on your memory.

Fault challenge. Introduce or analyse “The failure disappears after reset” as one bounded deviation. Inspect original symptom, histories, diagnostics, timestamps and active cause The working interpretation is that reset changed evidence or state without proving the initiating cause. The next proving action is to reproduce under a controlled condition and preserve pre/post-event data. Change only one condition before observing the result, and preserve timestamps or measurements where timing matters.

Review and recovery. The most common trap here is testing only one ideal sequence. After restoring the cause, repeat the normal case and at least one stop, timeout, disconnect or restart boundary relevant to this topic. Remove temporary forces and bypasses, return the model to a known state and retain the evidence that both operation and recovery are deliberate.

Explain it aloud: Why test faults and restart behavior? A defensible short answer is: Because a syntax, compile, runtime, mapping or target mismatch found through the same case or target licences, device descriptions, libraries, task configuration, operating system and commissioning access can expose assumptions that never appear during ideal startup and steady operation.

Case 05

predict → observe → prove

Prove diagnose a controlled fault

Engineering context. a syntax, compile, runtime, mapping or target mismatch found through the same case. Preserve the first symptom, divide the system at a measurable boundary and change one condition only after predicting the result. Begin with a written normal condition and identify which request, state, physical result or communication value will provide independent confirmation. Do not begin by changing the configuration; the initial state is part of the evidence and should remain reproducible.

Controlled setup. Use the “Isolate one failure” stage of the workflow: introduce or analyse a syntax, compile, runtime, mapping or target mismatch found through the same case and locate the first disagreement. The acceptance record should show this result: the proving action distinguishes the leading hypotheses. Record initial conditions, the exact stimulus and the observation point so another learner can repeat the case without relying on your memory.

Fault challenge. Introduce or analyse “Simulator and target disagree” as one bounded deviation. Inspect model boundary, software version, task timing, I/O behavior, data types and configuration The working interpretation is that a learning model and the intended target do not share one of the recorded assumptions. The next proving action is to reduce the case and verify against current target documentation. Change only one condition before observing the result, and preserve timestamps or measurements where timing matters.

Review and recovery. The most common trap here is resetting, forcing or replacing before evidence is retained. After restoring the cause, repeat the normal case and at least one stop, timeout, disconnect or restart boundary relevant to this topic. Remove temporary forces and bypasses, return the model to a known state and retain the evidence that both operation and recovery are deliberate.

Explain it aloud: Can browser practice replace official software or hardware? A defensible short answer is: No. It can build concepts and diagnostic reasoning. Exact firmware, I/O electrical behavior, networking, safety and commissioning require current official tools, documentation and target equipment.

Case 06

predict → observe → prove

Prove transfer and hand over

Engineering context. the learned behavior ported, compiled and accepted in the required target toolchain. Restore normal state, remove temporary changes, repeat affected checks and document which claims remain limited to the learning environment. Begin with a written normal condition and identify which request, state, physical result or communication value will provide independent confirmation. Do not begin by changing the configuration; the initial state is part of the evidence and should remain reproducible.

Controlled setup. Use the “Close the evidence loop” stage of the workflow: complete the learned behavior ported, compiled and accepted in the required target toolchain and repeat the affected regression cases. The acceptance record should show this result: an evaluation is complete when the same representative job is tested in each candidate and differences are recorded as evidence rather than inferred from feature labels. Record initial conditions, the exact stimulus and the observation point so another learner can repeat the case without relying on your memory.

Fault challenge. Introduce or analyse “The result cannot be explained” as one bounded deviation. Inspect prediction, observation, proving action, alternative hypotheses and limitations The working interpretation is that activity occurred but the evidence is not yet transferable or reviewable. The next proving action is to have the learner defend the signal path and repeat a changed case. Change only one condition before observing the result, and preserve timestamps or measurements where timing matters.

Review and recovery. The most common trap here is treating an acknowledged message or one successful rerun as handover. After restoring the cause, repeat the normal case and at least one stop, timeout, disconnect or restart boundary relevant to this topic. Remove temporary forces and bypasses, return the model to a known state and retain the evidence that both operation and recovery are deliberate.

Explain it aloud: How should progress be documented? A defensible short answer is: Keep the requirement, initial state, program or configuration, observed values, fault hypothesis, proving action, recovery result and a concise limitations statement.

Answer surface / 07

Questions people ask about CODESYS versus a browser PLC simulator

These concise answers define the operating, training and product boundaries most often missed in broad summaries. The full workflow and diagnostic table above provide the evidence behind them.

What should I learn first about CODESYS and guided browser PLC simulation?

Start with the operating contract and evidence path: whether the goal is guided learning, iec project development, target deployment, visualization or device integration, followed by ide, runtime, target packages, iec languages, libraries, machine model, grading and platform requirements. Add advanced features only after the baseline is predictable.

How do I practise CODESYS and guided browser PLC simulation effectively?

Use short cases with known initial conditions, a written prediction, one action and an observable result. Then alter a boundary or fault and explain why the evidence changed.

What counts as proof of competence?

A repeatable artifact or system result plus an explanation of the signal path is stronger than time spent, screenshots or a copied answer. Physical competence requires separate supervised evidence.

Why test faults and restart behavior?

Because a syntax, compile, runtime, mapping or target mismatch found through the same case or target licences, device descriptions, libraries, task configuration, operating system and commissioning access can expose assumptions that never appear during ideal startup and steady operation.

Can browser practice replace official software or hardware?

No. It can build concepts and diagnostic reasoning. Exact firmware, I/O electrical behavior, networking, safety and commissioning require current official tools, documentation and target equipment.

How should progress be documented?

Keep the requirement, initial state, program or configuration, observed values, fault hypothesis, proving action, recovery result and a concise limitations statement.

What should I do when the answer differs from a guide?

Check assumptions, version, units and initial state first. Reduce the case, compare one boundary at a time and prefer current primary documentation for target-specific behavior.

When is a CODESYS and guided browser PLC simulation exercise finished?

An evaluation is complete when the same representative job is tested in each candidate and differences are recorded as evidence rather than inferred from feature labels.