Codesys 4 Is Released!

The next generation of the Codesys IDE has been released! Codesys 4 is a web-based software suite that now supports Windows and Linux operating systems.

You should read the entire release notes and feature lists: https://www.codesys.com/products/engineering/codesys-4/

It is important to read and understand the part in yellow highlighted below, Codesys 4 is NOT YET a direct replacement of Codesys 3.5.

What version 1.0.0.0 does not yet include

Development began with the foundation: file-based storage, separation of the user interface and background processes, command-line invocation, and an extension model. The feature set continues to grow with each version.

There are two distinct levels to consider here.

Outside of these two use cases, CODESYS 3 remains your tool. This applies to everything beyond Structured Text, Ladder Diagram, and Modbus TCP—such as the other IEC 61131-3 languages, additional fieldbuses, visualization, motion, and safety.

Even within these two use cases, there are still features missing that you are familiar with from CODESYS 3. These include online functions for the running controller (online changes, breakpoints, forcing variables), convenience features for editing (including refactoring, cross-reference lists, and project-wide undo and redo), quality assurance tools (including Test Manager, static analysis, automated module tests, and library documentation generation), as well as extensions from external partners with their own editors and configurators. These missing features are known and are being addressed step by step.

The specific features included in each version are listed in the release notes and in the online help for that version. The semi-annual CODESYS Feature Briefing provides an outlook for the next six to twelve months.

Installation of Codesys 4

Download the suitable installations files according to your preferred operating system. One of the interesting future features is a C4-Server, which is a team solution for running a LDAP controlled Codesys solution on a server.

Being a web-based solution, the entire program is no longer delivered in the Codesys installer. In fact, I miss that Codesys 4 is included in the Codesys Installer, that has helped bring order in the different versions of Codeys 3.5 that I have installed.

Install the missing libraries and .NET prerequisites from Microsoft: https://dotnet.microsoft.com/en-us/download/dotnet/thank-you/runtime-desktop-8.0.31-windows-x64-installer

First Impressions of Codesys 4

The initial impression is that too much space is wasted on round corners, and smart icons. I instantly miss the highly functional design of Windows 2000 era that we all know from the Codesys 3.5 IDE.

Loads and loads of rounded corners and wasted space. I chose to Create Device Project, as no old Codesys 3.5 projects can be opened from that start of program.

Creating a new device project, putting anything in the Version field results in the shown red error. Not possible to create project without leaving this field empty. By experimentation, I found that the pattern “0.0.0” or “0.0.0.0” is accepted. Which would be nice to know in a tooltip, especially if creating a new library project, where the version field is mandatory.

I chose a PLC, it is nice to see that all supported packages comes in the program and that you do not have to install them separately.

Codesys 4 only supports structured text (ST) and Ladder Diagram (LD) from the initial version 1.0.0.0. CFC and FDB is first planned for releases in 2027.

Adding a Method to my initial PRG_PLC

The overall view of the IDE, after making a new project.

Dark mode is available, this is a nice new feature, fully implemented in all parts of the IDE.

“Format Document” puts everything in a nice order with correct indentations.

Ladder Diagram programming seems incredible clunky. Siemens had this mastered in S5 series of PLCs, on the Programmiergerät PG 7 series of computers and their programming environment. Why is somebody trying to reinvent Ladder Diagram programming in 2026 and make it worse. There isn’t even any CTRL+SPACE help on selecting variables.

Personally I think Codesys 4 should have postponed release, until CFC/FDB was implemented. It should have been released with a much larger drive to implement CI/CD, git etc. in existing Codesys 3.5 programs. If it was launched as a first step on bringing existing program into the future, instead of bringing a half implementation without online change, CFC and OPC UA.

I fear that the high functionality approach and user experience from Codesys 3.5 is being sacrificed to meet “demands” of web-based solutions and API/AI integrations. I never asked for this. In fact I have in multiply instances given Codesys feedback on please do not change the use and feel of Codesys IDE. It is near perfect. While Codesys 4 is released as a new part of the toolchain, and not a direct replacement of Codesys 3.5, I think we all can see where this is heading…

I fear the worst and hoping for the best never worked.