What is CODESYS 4?
Integrated, web-based development environment
CODESYS 4 is a new, web-based development environment for IEC 61131-3 programming. As a lean, platform-independent tool, it complements the proven CODESYS Development System 3, initially for library development in Structured Text. Additional features will be added on an ongoing basis over the next months.
Use case 1
CODESYS 4 for library development
Anyone who develops libraries for CODESYS controllers is familiar with the situation: version conflicts among team members, manual build steps, a powerful development system that offers more than is necessary for focused library work, and a Windows dependency that gets in the way on the company server or in the CI/CD process. CODESYS 4 is platform-independent and runs on all common operating systems. It can also be used in headless mode.
Typical Workflow: From the library to the automation project
Develop
Write your library in the ST Editor of CODESYS 4 or in the CODESYS Development System 3.
Versioning
Check your project directly into Git using file-based storage in text format, and compare changes in a way that makes them easy to track.
Automated build
Compile via CLI and integrate into a CI/CD pipeline: Every change is automatically built and tested against test cases.
Integration
Integrate the finished library into the comprehensive automation project in CODESYS Development System 3 and reuse it as needed by storing it in the library repository.
Release
The first release will be available in September 2026. You can use CODESYS 4 for free until at least the end of 2028. A paid licensing model will be introduced in 2029 at the earliest.
Use case 2
CODESYS 4 for simple applications
Those who build small machines, test benches, or device-integrated applications rarely need the full range of features; instead, they need a fast, seamless path from the project to the controller. A typical scenario: a CODESYS-native controller running on a Raspberry Pi, Linux hardware, or a Windows soft PLC, with a manageable number of I/Os connected via Modbus.
Typical Workflow: From the project to the controller
Create
Create a project in CODESYS 4 and select the CODESYS-specific target controller.
Program
Write logic in Structured Text and Ladder Diagrams using the modern ST Editor and the newly developed Ladder Editor.
Connecting I/Os
Set up a few digital and analog I/Os using the Modbus Configurator and map the I/O variables.
Load and monitor
Load the application onto the controller, monitor variables, and adjust parameters at runtime.
In the first version, only CODESYS-native runtimes are supported as target controllers: Raspberry Pi, Windows Soft-PLC, Linux, and Virtual Control for the simulation. Third-party hardware is not planned at this time.
This allows users to implement their first complete device projects without needing the full range of features offered by CODESYS Development System 3. Features such as online changes, debugging with breakpoints, ladder monitoring, and additional fieldbuses other than Modbus will follow in later releases. Until then, CODESYS 3 remains the right tool for these tasks. For simple application development and small projects, CODESYS 4 is ready for productive use right from the first version.
What does CI/CD mean for OT development?
CI/CD (Continuous Integration / Continuous Delivery) is a development approach from the IT world that is increasingly gaining traction in automation as well. Specifically, this means that when you change a function in your library, the code will automatically be compiled, tested against defined test cases, and released if successful. If a test fails, you will receive immediate feedback, regardless of who made the change.
Especially for projects that are developed over a longer period of time, this process prevents errors from creeping in or documentation from becoming outdated. Automated and documented development processes also make it easier to meet compliance requirements, such as those under the Cyber Resilience Act.
Interaction between CODESYS 4 and CODESYS 3
CODESYS 3 is and will remain the comprehensive tool for automation, featuring motion control, fieldbus stacks, visualization, and many powerful convenience functions. It will continue to be developed and maintained for the foreseeable future.
CODESYS 4 complements the Development System 3 as a lean, focused environment, initially for library development in Structured Text. Whereas the CODESYS Development System operates as a full-featured Windows application, CODESYS 4 relies on a browser-based front end, text-based storage, and CLI integration.
Features
The initially limited feature set is a deliberate choice: The new architecture (file-based project storage, separation of front and back end, CLI, extension model) provides a future-proof foundation on which the feature set will grow with each release.
Would you like to test CODESYS 4 as an Early Adopter? Then fill out this form and click "Submit".
Curious?
Further information can be found in the interview with Kevin Ketterle.