---
title: X4 types, results and methods
summary: Lua, LuaJIT FFI, identifiers and MD: values accepted and returned by code.
section: reference
kind: guide
status: reference
updated: 2026-10-26
tags: ["API","X4"]
sources: ["https://wiki.egosoft.com/X4%20Foundations%20Wiki/Modding%20Support/","https://www.lua.org/manual/5.1/manual.html","https://luajit.org/ext_ffi_api.html"]
---
## Types

Types and methods refer to Lua 5.1 / LuaJIT and X4 layers, rather than other games. XML attribute types have a [separate XSD schema reference](wiki:schema-types).

- [string - Strings](wiki:type-string)
- [number - Numbers](wiki:type-number)
- [boolean - Booleans](wiki:type-boolean)
- [table - Tables and methods](wiki:type-table)
- [function - Functions and callbacks](wiki:type-function)
- [nil - Missing values](wiki:type-nil)
- [cdata - C values and FFI](wiki:type-cdata)
- [userdata - Opaque objects](wiki:type-userdata)
- [thread - Coroutines](wiki:type-thread)
- [ids - X4 identifiers](wiki:type-ids)
- [md-values - Mission Director values](wiki:type-md-values)
- [results - any, unknown, none and multiple results](wiki:type-results)