Runs in your browser

PLC Simulator — free, online, no download

TryPLC is a PLC simulator that executes IEC 61131-3 Structured Text and ladder logic directly in the browser. You write the program, force the inputs, and watch the variables change scan by scan — no licence key, no virtual machine, no vendor installer.

Open the simulatorLadder logic canvas

What the simulator actually does

IEC 61131-3 Structured Text engine

A scan-cycle interpreter written for the browser — not a video of a PLC. It parses declarations, executes IF / CASE / FOR / WHILE, resolves expressions with IEC operator precedence, and updates outputs every 100 ms just like a real cyclic task.

Standard function blocks

Timers (TON, TOF, TP), counters (CTU, CTD, CTUD), edge detection (R_TRIG, F_TRIG), bistables (SR, RS) and the math/comparison blocks behave to the standard, including retained instance memory between scans.

Live variable watch and forcing

Every declared variable appears in a watch grid with its live value. Double-click a BOOL to force it, type a new value into an INT or REAL, and watch the logic react on the next scan — the same workflow as an online connection in TIA Portal or CODESYS.

Breakpoints and step debugging

Set breakpoints and watchpoints in the editor, pause the scan, and inspect state line by line. Executed lines are highlighted so you can see exactly which branch the logic took.

Ladder logic simulator

A separate ladder canvas draws rungs with contacts, coils and inline function blocks, simulates power flow across them, and generates the equivalent Structured Text so you can compare both languages side by side.

Nothing to install

No licence file, no virtual machine, no vendor download. The simulator runs entirely in the browser tab, so it also works on a locked-down work laptop or a tablet.

How a simulation run works

  1. Declare your variables. Inputs, outputs and internal memory go in the VAR grid, which parses as you type and becomes your watch table.
  2. Write the program. Structured Text with syntax highlighting, context-aware completion and inline diagnostics from the built-in analyser.
  3. Build. The compiler reports declaration, type and syntax errors before anything runs; a failed build stops execution instead of producing misleading behaviour.
  4. Run the scan cycle. The engine executes the program repeatedly, so timers accumulate, counters retain and edge detection fires for exactly one scan.
  5. Force and observe. Toggle inputs from the watch grid and confirm the outputs move the way your logic intends — then fix what does not.

Who uses a PLC simulator, and why

Students
Practise the exercises from an automation course without waiting for lab time on shared hardware.
Career changers
Get hands-on with real PLC syntax before an interview, instead of only reading about it.
Working technicians
Prototype a sequence, prove a timing question, or test a rung before touching the live machine.
Trainers
Share a link to a running example — no site licence, no lab installation, no version mismatch.

Where the simulation stops

A simulator is only useful if you know its edges, so here are ours:

  • It simulates logic, not hardware. There is no real I/O bus, so wiring faults, module diagnostics and field-device behaviour are modelled, not measured.
  • It is vendor-neutral IEC 61131-3. Vendor-specific extensions and libraries from Siemens, Rockwell or Beckhoff are not reproduced one for one.
  • It is not a safety or validation tool. Always commission logic on the target controller before production use.

Where to go next