How to change the difficulty of a terraria server

To change your world difficulty, you will need to create a new world since the one that has been generated used the default difficulty. Follow these instructions :

• Stop your server
• Change your world name in the "settings" page
• Change the difficulty in the "settings" page
• Go back to the manage page and click "restart"

If you don't want to generate a new world, you can still use a tool called TEdit to change your world difficulty.
Once the difficulty changed, you can set the right difficulty of your Terraria server and upload your modified world to the server.