If your hardware vendor (e.g., a small Chinese PLC maker) only provides a 2.3 runtime, you can use the free IDE to develop the entire PoC in simulation. Only when you move to production do you buy the runtime key.
| Feature | CODESYS 2.3 Free | CODESYS 3.5 Free | | :--- | :--- | :--- | | | Free | Free | | Simulation | Free (Win32 target) | Free (SoftPLC on PC) | | User Interface | Classic, functional, dated | Modern, ribbon-based, customizable | | Visualization | Basic (paid upgrade) | Powerful web-based visualizations (Free for up to 2 users) | | Object-Oriented Programming | No (No methods, interfaces, inheritance) | Yes (Full OOP support) | | Git / Version Control | Very difficult (binary files) | Native Git integration | | Learning Curve | Steep (less intuitive) | Moderate (better help system) | | Target Hardware | Legacy PLCs (2005–2015) | Modern PLCs (2015–present) | codesys 2.3 free version
If you are a student or a new engineer starting from scratch, skip CODESYS 2.3 and download the free CODESYS 3.5. However, if you are maintaining a factory full of legacy machines, the 2.3 free version is indispensable. If your hardware vendor (e