CGNS File

What are CGNS files and how to open them

Are you having problems opening a CGNS 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 CGNS files.

What is a CGNS file?

A .CGNS file is a CFD General Notation System Data file.

CFD General Notation System Data files store detailed computational fluid dynamics information, including grids, flow fields, boundary conditions, equation definitions, and auxiliary data. They follow a standard for recording and retrieving CFD (Computational Fluid Dynamics) data defined by the CFD General Notation System (CGNS) project, which aims to make CFD data exchangeable between different software, platforms, and institutions. The CGNS standard comprises both the formal conventions (data model, naming, structure) and open-source software libraries for reading, writing, and modifying compliant data.

These files are generated by CFD programs, mesh generators, or post-processing tools using the CGNS software libraries. They can store data in either the ADF (Advanced Data Format) or HDF5 database formats, with HDF5 currently recommended for its broader tool support, compression and parallel I/O capabilities. The data is organized as a hierarchical tree of nodes; each node has a name, label, data type, dimensions, and possibly child nodes. The conventions for what to record and where ("Standard Interface Data Structures" or SIDS) and how it is laid out in the tree ("File Mapping") are specified in CGNS documentation.

Files begin with a distinctive byte-signature: at offset zero there is a line containing the ASCII text "ADFDatabaseVersionA02011.AdF0" preceded by four bytes C0 A8 A3 A9, identifying the Advanced Data Format variant used by some CGNS/ADF files.

How to open CGNS files

Important: Different programs may use files with the CGNS file extension for different purposes, so unless you are sure which format your CGNS 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: August 31, 2026

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