An H4 file is a data file saved in the Hierarchical Data Format (HDF). It typically contains arrays of multidimensional data, tables, or raster images. H4 files are commonly used to store scientific data and are used in environmental science, neutron scattering, non-destructive testing, and aerospace applications.

Two commonly used versions of HDF include HDF4 and HDF5 with each version including software libraries that contain functions for analyzing and manipulating data. Files saved in the HDF4 version are saved as an H4 or HDF4 file. Files saved in the HDF5 version are saved as an .H5 or HDF5 file. NOTE: The HDF Group maintains a list of programs that can read and process H4 files. One common open source option is GDAL - The Geospatial Data Abstraction Library.