Do not download firmware intended for the S4 "Active," "Mini," or "Zoom" variants. They are not compatible with the standard S4.
However, if you are looking to update an old S4 to the latest possible official version, or if you are interested in custom software (ROMs) to modernize the device, the information below will be useful. samsung s4 software update download
If you are trying to update an old S4 and encountering errors: Do not download firmware intended for the S4