It is not possible to save a PLAXIS file in a format compatible with an older version. For example, when creating/saving a file in PLAXIS 2D 2023, it is not possible to open this file in PLAXIS 2D CONNECT Edition V21 or earlier.
Please note that PLAXIS is backwards compatible: PLAXIS files made with an older version can be opened and used in a more recent version of the PLAXIS Input program. However, due to some low-level changes, it might occur that in some cases not all data is fully compatible.
An example is the calculation result file for a project made with PLAXIS 2D/3D CONNECT Edition V21 and earlier: the input model is fully compatible and can be loaded in the latest PLAXIS versions (e.g. PLAXIS 2D/3D 2023.2), however, it is not possible to visualize the results due to the major changes in the material database and the unit system. The solution is to install PLAXIS CONNECT Edition V21 side-by-side with any latest PLAXIS version to allow for viewing the calculation results of the older PLAXIS projects.
Sometimes, you may want to send the PLAXIS data to another party that does not have access to the latest PLAXIS version. In such cases, you can always let the other user use the latest Output program to inspect your files: the Output program (prior to PLAXIS 2D 2015 and PLAXIS 3D AE/2015) can be used as a results viewer without a licence. To do so, you can have the other party install the latest PLAXIS version on their computer, or you enclose the Plaxis Output program called with your results.
For PLAXIS versions starting from PLAXIS 2D 2015 and PLAXIS 3D AE (2015), special free viewers are available. Please see the related article about the Plaxis Viewer - standalone program to view results.
For support of older file versions, please see the related article about Output project compatibility.
Plaxis Viewer - standalone program to view results [Downloads]
Conversion of PLAXIS 2D files [Tips and Tricks]
Output project compatibility [Tips and Tricks]