NetCDF has two main file formats:

  • the netCDF-3 file format which supports the netCDF Classic Data Model and
  • the netCDF-4 file format which supports the netCDF Enhanced Data model.

The netCDF-3 file format has two variants for a total of four file formats:

  • CDF-1 (aka netCDF-3 or classic) - supports the netCDF Classic Data Model.
  • CDF-2 (aka 64-bit Offset) - a variant of CDF-1 that removes some size limitations on variables and datasets, it supports the netCDF Classic Data Model.
  • CDF-5 (aka 64-bit Data or pnetcdf) - a variant of CDF-2 which adds support for 64-bit integer and unsigned integer data types. It supports the netCDF Classic Data Model plus the additional integer types.
  • netCDF-4 - supports the netCDF Enhanced Data Model. It is written using the HDF5 file format. It is restricted to a subset of HDF5 while also including additional metadata to represent aspects of the netCDF Enhanced Data Model that do not have a corresponding concept in the HDF5 data model.

For a detailed description and discussion of the CDF-1, CDF-2, and CDF-5 file formats, see the “NetCDF-3 File Formats” page. For a detailed description and discussion of the netCDF-4 file format, see the “NetCDF-4 File Format” page.

Experimental Support for Zarr and NCZarr

Both the netCDF-C and netCDF-Java libaries provide experimental support for the Zarr and NCZarr format. (The netCDF-Java library is currently limited to read-only access.)

  • The Zarr format maps to the netCDF Enhanced Data Model with a few limitations. The limitations are due to differences between the Zarr and netCDF data models.
  • NCZarr datasets are Zarr datasets with a metadata convention to capture netCDF data model information not supported by the Zarr data model.

For a detailed description and discussion of netCDF support for Zarr and NCZarr, see the “NCZarr” page.

Read-Only Support for OPeNDAP

NetCDF supports read-only access to the OPeNDAP Data Access Protocols (DAP-2 and DAP-4). Both DAP-2 and DAP-4 are mapped to the netCDF Enhanced Data Model.

For a detailed description and discussion of netCDF support for OPeNDAP, see the “OPeNDAP” page.

Other File Formats Supported Read-Only by NetCDF-C and -Java Libraries

The netCDF-C library supports HDF-4 SD format files and … For a full list see the netCDF-C File Format Support page.

The netCDF-Java library supports HDF-4, GRIB, BUFR … For a full list see the CDM File Types page.