factorio-modding

name	factorio-modding
description	Use when creating, editing, or debugging Factorio mods — writing prototypes in data.lua, handling events in control.lua, defining mod settings, structuring info.json, writing locale files, or diagnosing desync and prototype errors.

Factorio Modding Reference

Mod Directory Structure

mod-name_version.zip (distribution)
└── mod-name/
    ├── info.json          # required
    ├── data.lua           # prototype definitions
    ├── data-updates.lua   # modify other mods' prototypes
    ├── data-final-fixes.lua
    ├── settings.lua       # mod settings prototypes
    ├── settings-updates.lua
    ├── settings-final-fixes.lua
    ├── control.lua        # runtime scripting
    ├── migrations/        # save migration scripts
    └── locale/
        └── en/
            └── strings.cfg

Mod folder name = internal mod identifier. Files beyond the entry points must be loaded via require().

---

info.json Schema

{
  "name": "mod-internal-name",
  "version": "1.0.0",
  "title": "Display Name",
  "author": "You",
  "factorio_version": "2.0",
  "description": "One line.",
  "dependencies": [
    "base >= 2.0",
    "? optional-mod",
    "! incompatible-mod"
  ]
}

Dependency prefixes: none = required, ? = optional, ! = incompatible.

---

Load Order & Lifecycle

Mods load by dependency depth, then alphabetically. Three sequential stages at game startup:

Stage 1 — Settings

settings.lua → settings-updates.lua → settings-final-fixes.lua
Only data and mods tables available. No prototypes yet.

Stage 2 — Data (prototype construction)

data.lua → data-updates.lua → data-final-fixes.lua
settings variable available. No game object. Only data:extend() calls persist — all other Lua state is discarded.

Create prototypes in data.lua (earliest) so other mods can modify them downstream. Use data-final-fixes.lua to safely override after all mods have run.

Stage 3 — Save Startup (per save load/create)

1. control.lua executes — register events, remote interfaces, commands. No game or storage yet.
2. on_init() — new saves only. Full game + storage access.
3. Migrations auto-run.
4. on_load() — existing saves. storage read-only. Only: metatable setup, conditional handlers, local references.
5. on_configuration_changed() — any config change. Full access.

---

Prototype Patterns (data stage)

-- Deep copy from base
local myArmor = table.deepcopy(data.raw["armor"]["heavy-armor"])
myArmor.name = "fire-armor"
myArmor.resistances = { { type = "fire", decrease = 20, percent = 80 } }
data:extend{ myArmor }

-- From scratch
data:extend{{
  type = "recipe",
  name = "fire-armor",
  enabled = true,
  energy_required = 8,
  ingredients = {{ type = "item", name = "copper-plate", amount = 200 }},
  results = {{ type = "item", name = "fire-armor", amount = 1 }}
}}

-- Modify existing
data.raw["container"]["iron-chest"].max_health = 1000  -- in data-final-fixes.lua

-- Access pattern
data.raw["<prototype-type>"]["<internal-name>"]

In-game: Shift+Ctrl+F while hovering an item opens the prototype explorer (internal name + type).

---

Event Handling (control stage)

-- control.lua
script.on_event(defines.events.on_player_changed_position, function(event)
  local player = game.get_player(event.player_index)
  if player.controller_type == defines.controllers.character then
    local inv = player.get_inventory(defines.inventory.character_armor)
    if inv.get_item_count("fire-armor") >= 1 then
      player.surface.create_entity{
        name = "fire-flame",
        position = player.position,
        force = "neutral"
      }
    end
  end
end)

Key namespaces: defines.events.*, defines.controllers.*, defines.inventory.*

---

Global State — storage table

Use storage (not bare globals) for any state that must persist across save/load and stay synced in multiplayer.

script.on_init(function()
  storage.my_data = {}
end)

script.on_event(defines.events.on_something, function(event)
  storage.my_data[event.player_index] = true
end)

---

Desync Prevention

Factorio is fully deterministic — all clients must produce identical state.

Cause	Fix
Globals mutated outside event handlers	Use storage table
Conditional event subscription	Always subscribe at module top level
Table reference as key (entity == other)	Use entity.unit_number as key
on_load doing too much	Only: metatables, local refs, conditional handlers

---

Locale Format

locale/en/strings.cfg — INI-style, not Lua:

[item-name]
fire-armor=Fire Armor

[item-description]
fire-armor=Burns the ground beneath you.

[mod-name]
fire-armor=Fire Armor Mod

Multiple languages: add locale/de/, locale/fr/, etc.

---

Common Errors

Error	Cause
unfinished string near '...'	Syntax error in data stage — check quotes/brackets
attempt to index field '?' (a nil value)	Wrong prototype type or name in data.raw
Unknown entity name: foo	Prototype not registered or typo in name field
Runtime error after save load	Syntax error in control.lua — doesn't prevent startup
Internal C++ crash	Engine bug — report with save + repro steps

---

Quick Reference

What	Where	API
Define new item/entity/recipe	data.lua	data:extend{}
Modify base game prototypes	data-final-fixes.lua	data.raw["type"]["name"].field = ...
React to gameplay events	control.lua	script.on_event(defines.events.X, fn)
Persistent cross-session state	control.lua	storage.key = value
Add mod settings	settings.lua	data:extend{{ type="bool-setting", ... }}
Cross-mod API	control.lua	remote.add_interface() / remote.call()
Keyboard shortcuts	control.lua	input.add_custom_input + handler

---

API Docs

• Prototypes: https://lua-api.factorio.com/latest/prototypes/
• Runtime: https://lua-api.factorio.com/latest/
• Data lifecycle: https://lua-api.factorio.com/latest/auxiliary/data-lifecycle.html
• Mod structure: https://lua-api.factorio.com/latest/auxiliary/mod-structure.html