What Is CODESYS? The Hardware-Independent IEC 61131-3 PLC Programming Software
What is CODESYS : hardware-independent IEC 61131-3 PLC programming software Open the manual for many European PLCs or industrial controllers and you will often find the name CODESYS in the software section, even when the hardware brands differ. That is because CODESYS is an automation programming platform that a large number of manufacturers have chosen as their software core. This article explains what CODESYS is, where it came from, which programming languages it supports, and why today's automation engineers should know it.
What is CODESYS? (In short)
CODESYS is software for programming automation control systems according to the IEC 61131-3 standard, developed by a German company. Its key strength is that it is not tied to any hardware brand. Hundreds of PLC and controller manufacturers worldwide build CODESYS into their devices, so engineers can learn one tool and program equipment from many brands. It supports Ladder, Structured Text, Function Block Diagram, SFC, and more.
Where does the name CODESYS come from?
CODESYS stands for Controller Development System. It was once written in mixed case as CoDeSys and is now written in all capitals. Pronunciation varies, with "co-de-sys" and "code-sys" both widely understood.
History of CODESYS and the company behind it
Founded in Kempten, Bavaria, Germany, as 3S-Smart Software Solutions GmbH by co-founders Dieter Hess and Manfred Werner, with a focus on software for automation systems.
CoDeSys became popular with controller manufacturers because it spared them from building their own programming software from scratch.
Restructured as the CODESYS Group, with software development clearly separated from sales and services, and more than 30 years in operation.
CODESYS Group structure
Administration and management · Kempten, Germany
Software research and development · Kempten, Germany
Sales, marketing, training, and support · Kempten, Germany
Subsidiaries under CODESYS GmbH
Milan, Italy
Beverly, Massachusetts, USA
Beijing, China
Beyond its own offices, CODESYS has distributors and partners around the world, which makes documentation, sample programs, and a user community easy to find.
Why is CODESYS so widely used?
According to CODESYS, hundreds of manufacturers use it in their products
From compact PLCs and machine controllers to industrial PCs
Built on an international standard, so programs are written the same way regardless of hardware brand
Many familiar automation brands, including WAGO, Festo, Lenze, ABB, Parker, and Weidmüller, use CODESYS as the software basis for some of their device families, while some major PLC makers still use their own proprietary software. For users, the benefit is that skills learned once apply across many brands, without long-term lock-in to a single supplier.
Which programming languages does CODESYS support?
IEC 61131-3 defines several languages for PLC programming. CODESYS supports all of them and adds one language of its own.
Looks like relay circuits, familiar to electricians, ideal for on/off logic and interlocks
A Pascal-like text language, ideal for complex calculations, loops, and data handling
Connects function blocks graphically with clear signal flow, well suited to process control
Divides work into steps and transitions, ideal for machines that run in sequence
A low-level, assembly-like language, deprecated in the third edition of IEC 61131-3 and mainly kept for legacy programs
A CODESYS extension that lets you place blocks freely on the canvas and set execution order yourself
Which language suits whom?
In Thailand and much of Asia, most PLC programmers come from an electrical background and prefer Ladder, while in Europe many engineers come from software and favor Structured Text. A key strength of CODESYS is that you can mix languages in a single project, for example Ladder for safety interlocks, ST for recipe calculations, and SFC for machine sequencing. Teams with different backgrounds can work together, and commissioning time on site is reduced.
Main components of CODESYS
| Component | Purpose |
|---|---|
| Development System | Write, test, and debug programs on Windows. Free to download, with a simulation mode for testing without hardware |
| Runtime (CODESYS Control) | The software that actually runs the program on a controller or industrial PC |
| Visualization / WebVisu | Build HMI screens in the same project and view them in a web browser |
| Fieldbus and communication | Supports EtherCAT, PROFINET, EtherNet/IP, CANopen, Modbus TCP/RTU, and OPC UA |
| SoftMotion | An add-on for multi-axis servo motion control |
| CODESYS Store | A source for libraries, add-ons, and sample projects |
Who should learn CODESYS?
- Automation engineers and technicians working with European machines or multiple controller brands in one plant
- Machine builders (OEMs) who want freedom to choose hardware without rewriting all their code
- Software programmers moving into automation, since Structured Text resembles general-purpose languages
- Students and beginners, because it is free to download and simulation mode lets you practice right away
Want to use an industrial PC instead of a PLC?
CODESYS also offers Runtime software that turns an industrial PC into a PLC. Read more in our article How CODESYS Runtime Turns an Industrial PC into a PLC.
Frequently asked questions (FAQ)
What is CODESYS?
CODESYS is German automation programming software based on IEC 61131-3. It works with PLCs and controllers from many brands and is not tied to any single manufacturer.
What does CODESYS stand for?
It stands for Controller Development System, a system for developing programs for controllers.
Is CODESYS free?
The CODESYS Development System is free to download. Runtime licenses and some add-ons may carry costs, depending on the hardware and features used.
Which languages does CODESYS support?
Ladder Diagram, Structured Text, Function Block Diagram, Sequential Function Chart, Instruction List, and the Continuous Function Chart extension.
Which PLC brands use CODESYS?
Hundreds of manufacturers, including WAGO, Festo, Lenze, ABB, Parker, and Weidmüller for certain device families. Always confirm with the manufacturer that your specific model supports CODESYS.
Need advice on CODESYS and automation control?
E-POWER engineers can help you choose controllers, design control systems, and connect machines to your plant's IoT and SCADA systems.
LINE: @epower info@epower.co.thTel. +66 81-559-5145 | YouTube: Epower Service | TikTok: epowerservice_
Related articles: How CODESYS Runtime turns an industrial PC into a PLC, PLC vs PAC, Modbus RTU vs Modbus TCP, Complete guide to industrial sensors
Company information: www.codesys.com
