Simulate GRAFCET online
A simulation plays your GRAFCET through. You press Play and see which step is active, which action is running, and which transition is waiting. Right in your browser, no installation.
How a simulation runs
Four steps, repeated in a loop
1. The initial step becomes active
When you press Play, the initial step activates. You recognize it by its double border. Active steps turn green.
2. The transition checks its condition
Below every step is a transition. Its condition is checked continuously. While it is waiting, the transition blinks yellow.
3. The transition fires
When the step before it is active AND the condition is true, the transition fires. The old step becomes inactive, the new step active.
4. The action runs
If a step is active, its action runs. A feedback connection can jump back to the beginning — and the loop starts over.
What you can control
Inputs, edges, time conditions and value comparisons
Variables
Set buttons and sensors like b1, s1 or Start to TRUE or FALSE in the variable panel. The simulation picks up the new value immediately.
Rising and falling edges
↑b1 fires only the moment b1 switches from FALSE to TRUE. ↓b1 fires when it switches back. Perfect for button presses.
Time-on delay
5s/X1 becomes true when step 1 has been active for five seconds. Build in waiting times without extra steps.
Time-off delay
b1/3s stays true for three seconds after b1 goes off. Useful for run-on functions.
Step references
X9 is true while step 9 is active. XM9 works the same way for macro steps. Use them to link multiple GRAFCETs.
Value comparisons
[C1≥8] or [Temp<50] check a numeric value. Ranges like [3≤C<10] work too.
What the colors mean
Spot at a glance what is happening
Green — active
The step or action is currently active. The green border and fill make it easy to see.
Yellow (blinking) — waiting
The transition is waiting for its condition. As soon as the condition becomes true, it fires.
Green — condition met
The transition condition is true. It is only waiting for all upstream steps to be active.
Red — conflict
Two alternative transitions would fire at the same time. IEC 60848 forbids this — you need to adjust the conditions.
These elements are simulated
Everything per IEC 60848 — including the advanced symbols
Initial step and step
The initial step with the double border starts the simulation. Every step turns green when it is active.
Transition
The transition checks its condition. The condition can be a button, a sensor, a time or a step reference.
Action (all types)
Continuous, stored (set/reset), pulse, time-delayed, time-limited and conditional — every action type is evaluated correctly.
Enclosing step
When an enclosing step becomes active, its sub-GRAFCET (the enclosure) starts. When it leaves, everything stops — including nested enclosures.
Macro step
A macro step represents a small GRAFCET on its own. Activation and end run automatically.
Source and sink transition
Source transitions (open at the top) start sequences without a preceding step. Sink transitions (open at the bottom) end sequences.
OR- and AND-divergence
At an OR-divergence exactly one branch continues. At an AND-divergence several branches run in parallel — and meet again later.
Feedback connection
A feedback connection jumps back to an earlier step. Loops without long lines.
Forcing order
A forcing order forces another GRAFCET into a defined state — empty, restarted, frozen or set to specific steps.
Frequently asked questions
Do I need an account to simulate?↓
No. The simulation is part of the free editor and runs immediately — no login, no limit.
Which standard does the simulation follow?↓
IEC 60848 (DIN EN 60848 in Germany). All rules of the standard are respected.
Do nested enclosures work?↓
Yes. An enclosing step can contain more enclosing steps. When the outer one ends, all inner ones end with it.
Can I change inputs while the simulation is running?↓
Yes. In the variable panel you set values to TRUE or FALSE live, or trigger single edges.
Are time conditions counted in real time?↓
Yes. Time-on and time-off delays run in real time. You can also adjust the speed.
Does the simulation work offline?↓
Yes. Installed as a PWA, grafcet.io runs without internet — the simulation runs in the browser.
Try it yourself
Open the editor, load the example GRAFCET and press Play. The simulation starts immediately.
Open the editor →