EU4 Modding Documentation

Description

Reference documentation for Europa Universalis IV modding. Use this skill when helping users create or modify EU4 mods, including new countries, governments, events, missions, religions, cultures, units, buildings, or any game content.

When to Use

Use this skill whenever the user asks about:

• Creating or editing EU4 mods
• Scripting events, decisions, or missions
• Adding new countries, cultures, or religions
• Modifying governments, estates, or factions
• Configuring units, buildings, or trade goods
• Writing triggers, effects, or modifiers
• Understanding EU4 mod file structure and syntax

Documentation Index

All documentation is in the docs/ directory. Each file is a self-contained reference page converted from the official Paradox Wiki.

| File | Topic | | --- | --- | | Advisor_modding.md | Creating and modifying advisor types | | Age_modding.md | Modding ages and age abilities | | Building_modding.md | Custom buildings and their effects | | Casus_belli_modding.md | Creating casus belli types | | Colonial_regions_modding.md | Colonial region and trade company definitions | | Country_creation.md | Creating new countries (tags, flags, history) | | Culture_modding.md | Adding and modifying culture groups | | Decision_modding.md | Scripting player decisions | | Defines.md | Global game constants (defines.lua) | | Diplomatic_action_modding.md | Custom diplomatic actions | | Disaster_modding.md | Scripting disasters | | Empire_of_China_modding.md | Mandate of Heaven / China mechanics | | Estate_modding.md | Creating and modifying estates | | Event_modding.md | Scripting country and province events | | Faction_modding.md | Government factions | | Government_modding.md | Government types and reforms | | Government_mechanic_modding.md | Special government mechanics | | Great_project_modding.md | Great projects (wonders) | | History_modding.md | Province and country history files | | Holy_Roman_Empire_modding.md | HRE mechanics modding | | Idea_group_modding.md | National idea groups | | Institutions_modding.md | Custom institutions | | Mercenaries_modding.md | Mercenary companies | | Mission_modding.md | Mission trees and tasks | | Modifier_modding.md | Country and province modifiers | | On_Actions.md | on_action hooks and event pulses | | Parliament_modding.md | Parliament mechanics | | Peace_treaty_modding.md | Peace treaty options | | Policy_modding.md | Idea group policies | | Rebel_modding.md | Rebel types and factions | | Religion_modding.md | Religions and religious mechanics | | Ruler_Personality_modding.md | Ruler and heir personalities | | Scenario_modding.md | Bookmark / scenario setup | | Scripted_function_modding.md | Reusable scripted functions | | Subject_type_modding.md | Vassal and subject types | | Technology_modding.md | Technology groups and levels | | Trade_company_modding.md | Trade company regions | | Trade_goods_modding.md | Trade goods and their modifiers | | Unit_modding.md | Land and naval unit types |

Usage Instructions

1. Identify the topic from the user's request (e.g. "add a new event" → Event_modding.md).
2. Read the relevant file(s) from the docs/ directory.
3. Answer using the documentation — syntax, required fields, and examples are all included.

For cross-cutting concerns (triggers, effects, scopes, modifiers), the most relevant files are:

• Event_modding.md — covers trigger/effect/scope syntax in depth
• Modifier_modding.md — all modifier keys
• Defines.md — hardcoded game constants you can override

Notes

• Source: Europa Universalis 4 Wiki
• Game version: EU4 (pages scraped 2026)
• All documentation applies to the Clausewitz scripting engine used by EU4