HDF4® is a library and multi-object file format for storing and managing data between machines. HDF4 is a very different technology than HDF5. The HDF Group recommends that, other than for working with existing HDF4 data, new applications use HDF5 since HDF5 addresses important deficiencies of HDF4.
If you’re interested in converting your data from HDF4 to HDF5, our engineers can help. Learn more about our consulting service or free and open source h4toh5 conversion tools.
NASA maintains a network of Earth Observing Satellites that transmit huge volumes of new imagery data daily in HDF4. As a result, HDF4 is used extensively in the Earth Sciences. The HDF-EOS Website, http://www.hdfeos.org has a wealth of information on these uses.
You can download HDF4, explore HDF4-related utilities and access HDF4 documentation here. Licensing and copyrights for HDF4 are here.