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cModLoader

cModLoader is a mod loader for most PC versions of vanilla Terraria. It's goal it to allow modders to easily get full access to Terraria and its code. So far its supported on Windows and Linux and works in most versions. It is not meant to replace tModLoader, in fact the original purpose of cModLoader was so mods could exist without the overhead/changes of tModLoader, which fundamental is very different then Terraria⁽¹⁾. cModLoader runs completely without 'modifying'⁽²⁾ Terraria's code (editing the original code). It makes use of Xna, FNA or Terraria itself to 'hook' functions and events to execute arbitrary code. This allows cModLoader to work without patches from MonoMod/Harmony, Mono.cecil or TerrariaInjector. Although cModLoader can run without patches, it contains a built in IL code patcher that uses Mono.cecil, which makes it easy to patch or replace a functions. These patches are done before the Terraria assembly loads therefore are safer then runtime patches⁽³⁾.

How cModLoader works

cModLoader is basically a wrapper for Terraria. When installing cModLoader the Terraria.exe file gets renamed and cModLoader takes its place. This then opens cModLoader when Terraria is opened from Steam or from a short cut. Because cModLoader is a wrapper it can basically control Terraria however it wants, for example, dlls are loaded by cModLoader rather then Terraria to allow mod dlls to load. And because cModLoader gets to run Terraria, its able to decide what occurs before Terraria starts like load content/mods or patch the Terraria executable. Most notably cModLoader does not reference Terraria, therefore can be built without needing Terraria, it technically uses reflection for everything but does some optimization to make it faster.
There is also an option to do a "virtual" lunch which does not move Terraria, so you could launch Terraria from steam and get vanilla and then launch Terraria from the cModLoader launcher to get modded.

Features

Although cModLoader does offer many features, its not meant to be tModLoader, and therefore does not contain many features like the ability to add items or other stuff. cModLoader offers, an IL patcher, config manager, launcher (very primitive), native window system for Windows (using Forms) and Linux (using SDL3 and partially SDL2), a custom Dynamic class meant to replace and improve reflection, and a lot more. Most of the features added are for comparability with every versions of Terraria such as a UI system that basically reimplements Terraria's UI while also being compatible with older versions that did not use the modern UI⁽⁴⁾. The native window system was also added because Linux Terraria can not run Windows Forms.

Mod Development

Developing a mod for cModLoader is fairly easy i think. It does basically requires you to know how Terraria works so if you don't, good luck. Basically you create a new c# project using .net Framework 4.5.2 and reference the cModLoader exe, you may also need to reference other Xna assemblies as well. First you need to inherit the cModLoader.ModComponents.PreMod class, this is used to do stuff before Terraria starts like define patches, its also where you say what Terraria versions your mod is compatible with. The RegisterMod() function is where you create a new instance of your mod which is a class that inherits cModLoader.ModComponents.Mod. From there you can do stuff, im sure you can figure it out, but keep in mind cModLoader is not tModLoader, you basically need to do almost everything. There may or may not be an example mod you can look at as well, cModLoader itself is a mod within itself so you can use cModLoader as a reference.
You can technically reference Terraria in your mod and use it like you would be with cModLoader or any other assembly however this will likely only work on the versions of Terraria you reference.

Future

The future of cModLoader is uncertain, on one hand it would be very useful to have a mod loader that works in any versions of Terraria. On the other, options to easily add items would be ideal, but its a lot of work required to make it work. cModLoader is affectively a boiler plate program at this point in development, it doesn't have much to show, other then it loads mods and uses Terraria's UI. I may consider adding the ability to add items, NPCs and more but for the time being its not the main goal of cModLoader.

History

cModLoader was created in 2025 original for Terraria version 1.4.4.9 as a way of loading mods. It was original created in c++ and used dll injection with unmanaged dlls to run code in Terraria. This versions was called cModLoader Legacy and is still available although does not work with modern Terraria.

Before cModLoader

Before cModLoader was even conceived, there was TerraHacker, a non-released memory reader/writer for Terraria. It was not capable of running normal code in Terraria but could modify memory to run arbitrary assembly code. It was shown off in Crawdad105's Discord server where it was capable of changing NPC textures and moving projectiles and in at least one Youtube video was capable of listing the number of NPCs in the game. TerraHacker came from "PlayerBase Finder"/"Health Hack", created in 2023, which could find the 'player base' (the memory location where the player class is located) and modify the player's health. This was also shown off in Crawdad105's Discord server on the 17th of September, 2023.

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