Around this time NASA investigated 15 different file formats for use in the Earth Observing System (EOS) project.

It supports a proliferation of different data models, including multidimensional arrays, raster images, and tables.

Supporting many different interface styles (images, tables, arrays) leads to a complex API.

Perhaps most importantly, the use of 32-bit signed integers for addressing limits HDF4 files to a maximum of 2 GB, which is unacceptable in many modern scientific applications.

[5] HDF5 simplifies the file structure to include only two major types of object: This results in a truly hierarchical, filesystem-like data format.

In addition to these advances in the file format, HDF5 includes an improved type system, and dataspace objects which represent selections over dataset regions.

The API is also object-oriented with respect to datasets, groups, attributes, types, dataspaces and property lists.