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There are 5 variants of the format known as "netCDF": (See https://www.unidata.ucar.edu/software/netcdf/docs/faq.html#How-many-netCDF-formats-are-there-and-what-are-the-differences-among-them)
- the classic format (aka netCDF3) CDF-1
- the 64-bit offset format with 32 bit record addressing (aka netCDF3) CDF-2
- Although the 64-bit offset format allows the creation of much larger netCDF files than was possible with the classic format, there are still some restrictions on the size of variables. It's important to note that without Large File Support (LFS) in the operating system, it's impossible to create any file larger than 2 GiBytes.
- Assuming an operating system with LFS, the following restrictions apply to the netCDF 64-bit offset format.
- No fixed-size variable can require more than 2^32 - 4 bytes (i.e. 4GiB - 4 bytes, or 4,294,967,292 bytes) of storage for its data, unless it is the last fixed-size variable and there are no record variables.
- When there are no record variables, the last fixed-size variable can be any size supported by the file system, e.g. terabytes.
- A 64-bit offset format netCDF file can have up to 2^32 - 1 fixed sized variables, each under 4GiB in size. If there are no record variables in the file the last fixed variable can be any size.
- No record variable can require more than 2^32 - 4 bytes of storage for each record's worth of data, unless it is the last record variable.
- A 64-bit offset format netCDF file can have up to 2^32 - 1 records, of up to 2^32 - 1 variables, as long as the size of one record's data for each record variable except the last is less than 4 GiB - 4. Note also that all netCDF variables and records are padded to 4 byte boundaries.
- 64-bit offset + 64 bit record addressing, (aka "64bit data") CDF-5. This format has no practical limits on data size.
- the netCDF-4 format
- the netCDF-4 classic model format
The 2 netCDF-4 formats require a netCDF4 library (with HDF5 underneath) to read. NetCDF-4 can read all 5 variants.
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