Free forever, and you may still not be allowed to use it

Search for free simulation software and you will find that almost every product in this category has a free edition, that most of them never expire, and that the pages describing them all read approximately the same. It looks like a solved problem with six equivalent answers.

It is not. The editions differ enormously, and they differ on something almost nobody checks before installing one.

What people compare, and why it is the wrong thing

The caps get compared. Thirty objects, three variables, ten agent types, a size limit. They are easy to find, easy to put in a table, and they are the least decisive thing on the page, because for a first real model almost any of these caps is survivable and you will know within a day whether yours is.

Two things matter far more, and neither is a number.

Whether you are allowed to use the output. A free edition licensed for learning and evaluation is not licensed for work, and that is a license term rather than a technical cap. Nothing stops you building the model. What stops you is that the answer belongs to a study you were not permitted to do.

Whether the edition can reach a conclusion. Some free editions build models and cannot run the comparison that was the point of building one. That is a functional limit, not a size limit, and it is usually further down the page than the object count.

Where they actually stand

Product	Free edition	Never expires	Commercial use
Bizagi Modeler	Bizagi Modeler	Yes	Permitted
ProcessModel	Personal License	Yes	Permitted
Arena	Student and demo edition	Yes	not stated
AnyLogic	Personal Learning Edition	Yes	Not permitted
FlexSim	FlexSim Express	Yes	Not permitted
iGrafx	None	—	—
Simio	None	—	—
Simul8	None	—	—

From the vendor records, rebuilt on every deploy. The full terms and what each cap actually stops you doing are on the tracker.

Of the products here that also sell a paid license, two publish a free edition whose terms allow use at work: ProcessModel, which says so, and Bizagi, whose freeware agreement is not limited to non commercial work. Several others forbid it or say nothing, and a free edition that says nothing has not told you that you may.

The table is generated from the vendor records rather than typed into this article, so it grows as the assessment does and it can never quietly disagree with the review pages it links to.

ProcessModel’s Personal License is the one that lets you use the work. A free trial starts on install, runs three days and extends to fourteen with an email sign-in, and then converts into a license that does not expire. The limits are on counts rather than on the size of the model: three variables, three attributes, one array and one scenario per model, six lines of action logic and six builder tiles per field, and runs of up to seven simulated days. There is no limit on how many activities, resources, entities, queues and routes a model holds, and the full results report stays. Its published terms permit commercial use. Seven simulated days will not cover a season, and one scenario means no side by side what-if cases. It will comfortably hold a service process, an approval flow, a clinic pathway or one line, which is the size of question most people bring to a first model.

Bizagi Modeler is free to an individual user, working locally on one machine. Its freeware agreement, a 2020 version, grants a perpetual license that is not limited to non commercial work, and bars only using the software to provide commercial IT services to third parties. What it does not give you is depth: the simulation reaches resources and calendars and stops short of the materials and batching a discrete event engine carries.

AnyLogic is the one to read closely before you start, because the Personal Learning Edition is genuinely capable and its license is genuinely restrictive. The agreement states that using the software, the models or the model output for commercial purposes or for research is prohibited. Not capped. Prohibited. It also carries technical limits: ten agent types, fifty thousand dynamically created agents, two hundred flowchart blocks per agent type, and a five hour ceiling on modeled time outside one library. An excellent way to learn the product, and not a way to answer a question at work.

FlexSim Express stops short of a conclusion. Free as the product’s default unlicensed state, capped at thirty objects, and models can be built and saved within that cap, which is more than a trial offers. But the publisher’s own documentation states that the Experimenter is disabled. That is the feature that runs a model repeatedly across scenarios and compares the results, which for most people is the reason the model exists. You can build. You cannot conclude, and the publisher limits the edition to testing, evaluation and viewing models.

Arena and ARIS publish an edition for learning or modeling rather than for work. Arena’s is a size limited demo and student edition: the student version prohibits commercial use, and the demo is described for proof of concept models and course exercises. ARIS Express is free, aimed at beginners and described as a modeling tool with no mention of simulation, so for the capability this page is about it is not shown to offer anything.

Simul8, Simio, iGrafx and SAP Signavio have no permanent free edition, which is a clean answer and one you would otherwise spend an afternoon establishing. Simio retired its Personal Edition in favor of a thirty day full-featured trial, and its free academic licenses are for non commercial work.

The caps, and what they actually stop

Since the caps are what everybody looks at first, here is what they mean in practice.

Thirty objects, the FlexSim Express cap, is roughly a process with thirty distinct activities, queues and resources, weighted towards physical items, since that is the kind of model the product is built for. A single line fits. A plant does not.

Three variables, three attributes, one array and one scenario, the ProcessModel cap, limits the logic and the what-if cases a model carries rather than its size. A process with a handful of parameters fits. A study that compares many cases side by side does not.

Seven simulated days, also ProcessModel, is one week of modeled time, which covers a weekly cycle and will not cover a season. AnyLogic’s Personal Learning Edition has a five hour ceiling on modeled time outside one library, which covers a shift and little more.

For a first model of one question, none of these will stop you finding out whether your process has a constraint and where it is.

How to actually use one

Read the license before the feature list. It is the one page that decides whether the work you are planning is permitted, and it takes two minutes. Every other question is recoverable later; this one is not.

Then check what is disabled, not just what is capped. A size limit tells you how big the model can be. A disabled feature tells you what you cannot do with it, and the second is what ends projects.

Build the smallest model that answers one question. Not the process. One question. Nearly every free edition holds a model of one question comfortably, and a first model that is too ambitious fails for reasons that have nothing to do with the caps.

And treat the free edition as the evaluation. A tool that can answer a real question at its free tier has told you something about how it will behave when paid for. A tool whose free edition cannot reach a conclusion has told you something too.

One thing we cannot tell you

What any of these cost once you outgrow the free edition. Only two of these publish a price on their own site, and one of those is the free product, so exactly one paid product here can be costed before you speak to anyone. We track that on a standing page. So the free edition is often the only part of the commercial relationship you can evaluate without a conversation. Know that before you invest a fortnight of modeling in one.