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Guides / Terraria / tModLoader mods

Switch a Terraria server from Vanilla to tModLoader

Switch a Vanilla Terraria server to tModLoader on the World page. Pick a 1.4.4 world, expect 1.4.5 worlds to be blocked, and switch back any time.

Updated , checked on Terraria tModLoader v2026.09.3.1

Open the World page, choose tModLoader under Server software, and choose Continue. The server runs tModLoader from its next start. Before you restart, check which world it will play: tModLoader runs Terraria 1.4.4 and cannot open a world that 1.4.5 saved.

The Terraria server page explains the three server programs: Vanilla, TShock and tModLoader.

Check your world first

A world that Vanilla or TShock saved with the current game is a 1.4.5 world. The World page lists each world with the game that saved it, for example “saved by Terraria 1.4.5”. A 1.4.5 world carries the tag Too new for tModLoader (1).

The Worlds list on a tModLoader server: worlds saved by Terraria 1.4.5 carry a red tag, one world saved by 1.4.4 has none
  1. Too new for tModLoader

You have three choices:

  • Pick a world that is not tagged, if you have one saved by 1.4.4.
  • Make a new world for tModLoader. See below.
  • Keep the 1.4.5 world and stay on Vanilla or TShock.

More on the tag: a 1.4.5 world will not open on tModLoader.

Switch

  1. Open the World page.
  2. In Server software, choose tModLoader.
  3. A box titled Run tModLoader? opens. It says that from the next start the server runs tModLoader, which downloads first, and that a world made or saved with 1.4.5 does not open on it. Choose Continue.
  4. In Worlds, choose Play this world on a world without the tag. Or make a new one with New world: give it a Name, Size, Difficulty, World evil and Seed, then Make this world. On tModLoader the world evil is random whatever you pick; only TShock follows it.
  5. Tell the players, using Message everyone on the Players page, then restart the server. A restart disconnects everyone who is on.
The Run tModLoader? box with Cancel and Continue, over the World page

The change takes effect at the next start. A running server is told “Restart the server for it to take effect.”

What happens at the first start

tModLoader downloads first, so the first start takes longer. It also sets up the .NET it needs. If it fails, start it again.

A new world is made at that start, and the server then plays it. If you restart on the old 1.4.5 world instead, the first start stops with the Crashes cause “The world is from a newer Terraria”.

Mods

The Mods page works once the server runs tModLoader. On Vanilla it says the server loads no mods and links to the World page. Add mods there, then apply. See the Mods page.

Players need tModLoader (free on Steam) to join. It downloads the server’s mods as they join.

Switch back

Each program keeps its own files, and the worlds are shared. To go back, choose Vanilla in Server software and restart. Nothing of tModLoader’s or Vanilla’s is lost.

A world that Vanilla or TShock saves with 1.4.5 is too new for tModLoader. If you switch back and forth, take a panel backup first. See the server’s Backups.

If it does not work

  • The server stops at start and the Crashes page says “The world is from a newer Terraria”. Pick a different world or make a new one, then start again.
  • Nothing changed after you switched. The change applies at the next start. Restart the server.
  • Players cannot join. They need tModLoader, not the normal game.

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