File Formats (Projects and Libraries)

Starting with version 2026.6, PLCnext Engineer uses new file formats.

These were introduced to optimize support for version control tools (improved mergeability, better comparability in the repository using diff tools) as well as for reduced memory consumption and improved performance.

Furthermore, the folder structure for the referenced libraries contained in the archive is preserved after extraction, ensuring that all references remain valid in the extracted project.

In the new uncompressed *.plcn2 files, unlike the legacy *.pcwef flat file, the project's folder structure (in PLANT and COMPONENTS) is preserved, and the document names are no longer truncated according to the 8.3 convention.

The new formats apply to the project file itself as well as library files. The table below compares the file extensions.

Project Type Legacy New Comment

Compressed Project *.pcwex *.plcnx2 If you open a legacy project in the current version of PLCnext Engineer, a copy of the project is automatically opened and converted (without a prior prompt). The original project remains unchanged in the project directory. A corresponding entry is generated in the Project Log.
Saving the legacy version is no longer possible.

Uncompressed Project *.pcwef *.plcn2 See table row above.

Project Archive *.pcweax *.plcnax2 Extracting legacy archives results in automatic conversion to the new project format.
Saving legacy archives is no longer possible.

User Library *.pcwlx *.plcnlx2 The legacy library formats can still be included and used for a limited transitional period, so that existing projects can continue to be used for the time being.
However, as of software version 2026.6, user-defined libraries can only be released in the new library format.

System Library *.pcwlx *.plcnlx2 Referencing legacy libraries is still supported for a limited time and will then be deprecated.

Project Type	Legacy	New	Comment
Compressed Project	*.pcwex	*.plcnx2	If you open a legacy project in the current version of PLCnext Engineer, a copy of the project is automatically opened and converted (without a prior prompt). The original project remains unchanged in the project directory. A corresponding entry is generated in the Project Log. Saving the legacy version is no longer possible.
Uncompressed Project	*.pcwef	*.plcn2	See table row above.
Project Archive	*.pcweax	*.plcnax2	Extracting legacy archives results in automatic conversion to the new project format. Saving legacy archives is no longer possible.
User Library	*.pcwlx	*.plcnlx2	The legacy library formats can still be included and used for a limited transitional period, so that existing projects can continue to be used for the time being. However, as of software version 2026.6, user-defined libraries can only be released in the new library format.
System Library	*.pcwlx	*.plcnlx2	Referencing legacy libraries is still supported for a limited time and will then be deprecated.