.EU4 File

The eu4 file extension is mostly known to be related to Europa Universalis IV grand strategy computer game from Paradox and used for the default saved game file format to store game progress.

How to open:

When placed in the default save game folder (user settings) you can load the position in the game and continue playing.

How to convert:

There does not seem to exist any way how you can convert .eu4 files to anything else.