# Configure worlds and server settings

> Manage player limits, world creation, passwords and safe version changes.

## Server configuration

Open **Server → Configuration**. Settings are written to `serverconfig.txt` after the node finishes the task. Restart to apply them.

- **World name:** selects `Worlds/<name>.wld`; use letters, numbers, spaces, underscores or hyphens.
- **World size:** Small, Medium or Large. Used only when creating a new world.
- **Difficulty:** Classic, Expert, Master or Journey. Used only when creating a new world; Journey worlds need Journey characters.
- **Maximum players:** 1–255. This is an admission limit, not a performance guarantee.
- **Server password:** leave empty for no password.
- **Welcome message:** displayed when players join.
- **World seed:** optional; used when generating a new world.

AppLaunch manages the port, world directory and mod directory. UPnP is disabled because ports are allocated by the hosting node. Use structured configuration for these supported settings. The file manager also exposes advanced files and mod configuration under `ModConfigs`.

## Bring your world

Stop the server first. Upload the `.wld` file into `Worlds` through Files or SFTP. For tModLoader also upload its matching `.twld`, the matching mods and required configuration. Set the world name to the filename without `.wld`, then start. Keep your original copy until you have joined and confirmed the world is correct.

## Change or update software

Back up first, then open **Installation**. Select Vanilla or tModLoader and an official release. Installation stops the server and replaces runtime files while retaining worlds and mods. Starting is a separate action. Version changes are explicit, not automatic restarts during play. Never open a modded world in Vanilla expecting mod content to survive. Downgrades may be incompatible; restore a compatible backup instead.

If a task fails, read the displayed error. Do not assume that a queued action succeeded.