Merit Modeler
Completely FREE
Data Modeling Tool

A free data flow diagram tool is software that lets you create Data Flow Diagrams (DFDs) at no cost. DFDs show how data moves through a system — from external entities through processes and data stores. Merit Modeler is a completely free desktop DFD tool that also supports flowcharts and use case diagrams, runs offline on Windows, macOS, and Linux, and requires no subscription or online account.

Merit Modeler supports three main diagram types:

• Flowcharts — for visualizing process steps and decision logic
• Data Flow Diagrams (DFDs) — for mapping how data moves between processes, data stores, and external entities
• Use Case Diagrams — for documenting how users or systems interact with software

All diagram types support notes, Markdown descriptions, Swim Pools, Swim Lanes, and custom styling with dark, white, or handwritten themes.

Yes. Merit Modeler is completely free — it is freeware with no time limit, no feature restrictions tied to payment, and no subscription. There is also an App Store version available for macOS. The only cost is zero. Merit Modeler is developed by the same team behind the Luna Modeler, Moon Modeler, and Galaxy Modeler professional tools.

A flowchart shows the sequence of steps in a process — decisions, actions, and their order — making it ideal for documenting workflows, algorithms, and procedures.

A data flow diagram (DFD) shows how data moves through a system between external entities, processes, and data stores — making it ideal for analyzing and documenting system architecture and requirements.

Flowcharts answer "what happens and in what order"; DFDs answer "where does the data come from, go to, and how is it transformed".

Yes. Merit Modeler is a desktop application that runs entirely on your local machine. No internet connection is required to create, edit, or export diagrams. Your files stay on your device and are never uploaded anywhere. This makes it suitable for environments with strict data security requirements.