.por (portable file format) is an export format of the SPSS software, developed to enable data transfer between different versions of SPSS working on different operating systems. The export function writes all variables to the .por file.
In the past, the Steinmetz archive (taken over by DANS in 2005) opted to use SPSS.por as a preferred format for the long-term sustainability of statistical data. This was at a time when most of the data archived were SPSS files. For a long time DANS continued the policy of using .por as the preferred format for sustainability. This policy was revised in May 2020.
SPSS por only guarantees interoperability between different versions of SPSS, not between different software packages. The format has no official specification. SPSS appears to be phasing out the .por format. The best way to store data sustainably is to store both the data and the data documentation in an ASCII format.
SPSS Portable is a non-preferred format for file type Statistical data.