UE4SS

UE4SS (RE-UE4SS - “Unreal Engine 4/5 Scripting System”) is the runtime that loads into Palworld and lets you script the game. It is the backbone of Lua scripting mods and also supports C++ mods, ships an object dumper, and provides an in-game console/log.

What it gives you

• A Lua scripting API - hook UFunctions (RegisterHook), find live objects (FindFirstOf/FindAllOf), read and write properties, spawn actors, and call game functions at runtime.
• Object dumps - generate a dump of the game’s classes, functions and properties so you know the exact names to hook and call. Indispensable when writing a mod.
• A console and logging - your main feedback loop while developing.

Using it with Palworld

• Use the Palworld-specific build, not upstream/dev UE4SS. UE4SS is rebuilt per game build, and for Palworld you want Okaetsu’s experimental-palworld RE-UE4SS release paired with PalSchema. Grabbing the generic dev/upstream build on 1.0 causes a Steam-ID mismatch bug (forced character-creation screen, mods never load) - see Compatibility & updates.
• Fix the usmap/Lua-types crash. Generating a .usmap or Lua types from the console can crash on UE 5.1 unless the correct MemberVariableLayout.ini is next to the UE4SS dll - see Common errors and Useful links.
• Lua mods declare UE4SS as a dependency. A player needs UE4SS installed for your Lua mod to run.
• Don’t double-load it. Installing UE4SS two ways in the same game install (for example a Workshop copy plus a manual copy) causes a double-load crash. Pick one.

Runtime scripting has sharp edges

Callback lifetime (garbage collection), RPC parameter types, and whether code runs on host vs client vs dedicated server are all real traps in UE4SS Lua. Budget time to learn them - see Lua modding in Palworld.

When to use it

Reach for UE4SS when you want behavior - custom logic, hooks, commands, reacting to events. If you only need to change values, a data mod is simpler; for new Blueprint content, use the Palworld Modding Kit.

Credits & references

• UE4SS / RE-UE4SS is developed by the RE-UE4SS project (github.com/UE4SS-RE/RE-UE4SS).
• Palworld-specific Lua tutorials and the general Lua workflow are credited on Lua modding in Palworld.