Global

In Factorio the term "global" refers to 2 different things:

• 1. Global variables in Lua - variables that are defined without the keyword local are global: https://www.lua.org/pil/14.2.html.
• 2. The global table each mod has access to - a table with the name global declared as a global variable that is persisted between map sessions.

During the lifetime of a mod it's frequently required to save mutable data. Although mods are free to store such data in any variable the game will not persist that data between saving and loading.

To address this Factorio provides the table global - a global table - that is serialized and persisted between saving and loading of a map. Each mod has access to its own instance of this table (global) so data stored does not need to use some unique name.

Only specific data can be saved and loaded using this table:

• Basic data: nil, strings, numbers, booleans
• Tables, but not meta tables; tables with metatables become plain tables when saved and loaded.
• References to builtin Factorio LuaObjects

Circular references are also handled properly.