COMPILED-LIBRARY File
What are COMPILED-LIBRARY files and how to open them
Are you having problems opening a COMPILED-LIBRARY file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your COMPILED-LIBRARY files.
What is a COMPILED-LIBRARY file?
A .COMPILED-LIBRARY file is a TwinCAT Compiled-Library file.
TwinCAT Compiled-Library files are precompiled library archives for the TwinCAT 3 PLC system made by Beckhoff Automation. They store software components - function blocks, data types, POUs (Programs, Function Blocks, Functions), metadata and documentation - in a compiled (binary) form so that the source code is hidden. Compiled libraries are installed in the TwinCAT Library Repository, and are referenced by TwinCAT projects in order to reuse proven, versioned PLC code without exposing its implementation.
Creation happens within a TwinCAT 3 PLC project: the developer sets required library metadata (company name, title, version) and optionally visibility settings for library-internal items. Choosing "Save as library (compiled)" produces a compiled library instead of a source (editable) library. Compiled libraries offer protection of intellectual property. When used in a project, individual library elements cannot be opened for editing, but TwinCAT allows documentation (via comments or reStructuredText) to be included so that users can see descriptive information.
Internally, these files begin with the ASCII "PK" at the start (bytes 0x504B0304), indicating a ZIP-style container. They contain identifiable internal strings such as "__LANGUAGEMODEL.AUXILIARYPK", "AUTOMATICALLY GENERATED BY", ".OBJECTPK", and ".METAPK" which help tools detect them.
How to open COMPILED-LIBRARY files
Important: Different programs may use files with the COMPILED-LIBRARY file extension for different purposes, so unless you are sure which format your COMPILED-LIBRARY file is, you may need to try a few different programs.
We have not yet verified any programs for Windows that work with this specific file format. If you know one, please use the 'Suggest a program' link below. Thanks!
Last updated: September 2, 2026
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