Stop Biome Spreading on Your Terraria Server

The Corruption, the Crimson and the Hallow slowly convert the blocks around them, and a world that isn't watched can end up mostly infected. TShock can stop the spread for any of the three. These switches aren't in the Server Settings tab, so you set them in the config file. Journey worlds have a second, in-game way.

Checked against TShock 6.2.1 (Terraria 1.4.5.8), October 2026.

Stop the spread with TShock

TShock has one setting for each biome, and all three default to true, which lets the biome spread:

1. Start the server once if it has never run, because TShock writes its settings file on the first start.
2. Open the File Manager, go into the tshock folder and select config.json.
3. Press Edit. The settings sit together under "Settings", so scroll to find each name.
4. Change true to false on the lines you want. To stop everything, change all three.
5. Press Save, then restart the server from the Console tab.

Manage your server files explains the editor, and it is wise to create a backup first. Keep the commas and quotation marks exactly as they are. The file is JSON, and the Server Settings tab shows an error when it isn't valid.

TShock's documentation describes these settings as allowing each biome to spread "when a world is in hardmode". In TShock's code they block a biome's blocks from spreading in two places: the Hardmode tile update, and every attempt of that biome's grass to spread, which TShock's code comment describes as "Fired when grass is attempting to spread." Terraria's wiki says the spread before Hardmode is carried by grass, so these settings stop that too.

What it doesn't do

Turning a setting off only blocks new spread. It doesn't clean up blocks that are already infected. If a biome has already crept into your base, you will need to deal with it in game.

It also doesn't switch off Hardmode. If you would rather the world never entered Hardmode at all, the Hardmode off switch in the Gameplay section of the Server Settings tab stops the Wall of Flesh from starting it. TShock's description is: "Defeating the Wall of Flesh no longer starts Hardmode."

Stop the spread in a Journey world

A Journey world has an Infection Spread toggle in the Power Menu. Terraria's wiki describes it as preventing the spread of the Corruption, the Crimson and the Hallow, without reversing it. It doesn't stop the diagonal stripes of Hallow and Corruption or Crimson that appear when Hardmode begins.

On TShock the toggle is behind a permission, tshock.journey.biomespreadfreeze, which only the trustedadmin and owner groups have by default. Enable Journey mode on your Terraria server shows how to grant it. On tModLoader it is the journeypermission_biomespread_setfrozen line in serverconfig.txt, covered in the same guide.

If the biomes still spread

• Reopen config.json and check the lines say false, spelled in lowercase and with no quotation marks.
• Check you restarted after saving. TShock reads the file when it starts.
• tModLoader has no TShock settings, so the config file route doesn't apply there. Use a Journey world, or switch the server to TShock as Get started with your Terraria server describes.