# Launching Nx Witness in Compatibility Mode

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Compatibility mode lets you launch a compatible version of the client application in order to connect to a server running a different version of Nx Witness. The client downloads another version of itself to match the server version using the same algorithm as auto-update.

This would be necessary, for instance, when Nx Witness is installed at multiple sites (home, work, etc.) and only one installation has been upgraded to the current version. In that particular case, the System will have different versions and one client should connect to another System (client at home connects to System at work). Systems of different versions are highlighted in red in the login dialog and in yellow on the Welcome Screen.

When a client is connected to a server, all component versions are checked and a warning will open if the component versions differ from one another. A message will open specifying the version for the client and server, and prompting you to restart in compatibility mode. Click Restart to connect to the server.

In some instances, it may be necessary to download additional files for the compatibility pack. Once the download is complete, the client should be restarted.

IMPORTANT: The best practice is to have the same product version installed on all System components. If some of the components (server or client) in a multi-server System have different versions installed there may be operational issues.

See Upgrading Nx Witness for more information.