NetCDF Java Library

The NetCDF-Java Library is a Java interface to NetCDF files, as well as to many other types of scientific data formats. 

The library is freely available and the source code is released under the (MIT-style) netCDF C library license. Previous versions use the GNU Lesser General Public License (LGPL).

The preferred place to ask questions, discuss problems and features and get support is in the NetCDF-Java email list, which you can subscribe to from this page. Also you might want to search or browse previous netCDF-Java support questions.


The NetCDF-Java library implements a Common Data Model (CDM), a generalization of the NetCDF, OpenDAP and HDF5 data models. The library is a prototype for the NetCDF-4 project, which provides a C language API for the "data access layer" of the CDM, on top of the HDF5 file format. The NetCDF-Java library is a 100% Java framework for reading netCDF and other file formats into the CDM, as well as writing to the netCDF-3 file format. Writing to the netCDF-4 file format requires installing the netCDF C library. The NetCDF-Java library also implements NcML, which allows you to add metadata to CDM datasets, as well as to create virtual datasets through aggregation.

Which jar files do I need? Most needs can be fulfilled using netcdfAll.jar or toolsUI.jar. See Jar Dependencies for full details.

CDM/TDS source is now hosted on GitHub. To build the latest stable version from source or contribute code to the THREDDS project, see here.

Current stable release version 4.3 (requires Java 6)

Development branch version 4.5 (requires Java 7)

File format types

The NetCDF-Java library can read these file types and remote access protocols.

Note to GRIB users:

If you are depending on the CDM/TDS to read GRIB files, you must upgrade to 4.3+ AND closely examine the output of any files that you really care about. Check parameter names and everything else against the original documentation if possible, especially if there is any local parameter use. Please send us any files you suspect might be incorrectly read by the CDM library. Note that we will not backport fixes to version 4.2. Note that the variable names in 4.3+ will be different from those in 4.2.

Evolving documentation for GRIB is at:

Caveats and not-so-stable APIs:

Related Documents:


WebEx demo

You may need to first download the free WebEx Player.

CF Conventions

Coordinate Systems

Working notes and documentation on the coordinate system layer of the CDM

Feature Types

Working notes and documents on the scientific feature type layer of the CDM

Streaming NetCDF (Experimental)

Software libraries used by the Netcdf-Java library:

Applications using the Netcdf-Java library (partial list):

Miscellaneous Resources

This document was last updated June 2014