You should know that every netcdf-4 file is a legal hdf5 file, but not every hdf5 file is a legal netcdf-4 file. So, the file.nc was deliberate to show that the result is a legal netcdf-4 file. You can see some of the differences by doing the following commands: h5dump file.hdf5 and h5dump file.nc =Dennis Heimbigner Unidata Ticket Details =================== Ticket ID: NNZ-516447 Department: Support netCDF Priority: Normal Status: Closed =================== NOTE: All email exchanges with Unidata User Support are recorded in the Unidata inquiry tracking system and then made publicly available through the web. If you do not want to have your interactions made available in this way, you must let us know in each email you send to us.