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Map exchange string format

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This is a technical description of the map exchange string format, used to share map generating configurations with other users.

Factorio line wraps the entire map exchange string after 55 characters during export, but ignores all whitespace during import. The outer layer of the map exchange string format includes three angle brackets on either side: ">>>" and "<<<", which must be present for Factorio to accept the string. Between those two tokens is the map exchange data, encoded using base 64 as defined by RFC 4648 (or 3548, 2535, 2045, 1421, et al). All numerical values are stored in unsigned little-endian format.

This document will use the terms "int" to refer to 4 byte numbers and "short" to refer to 2 byte numbers. Boolean is a single byte that represents true if equal to 1, otherwise it is equal to false. Strings are Pascal-style int length prefixed strings. The format described below is valid at least for Factorio 0.14.x, other versions may use a different encoding scheme.

Factorio 0.14.x and beyond

short[4] The version string of Factorio that generated this string, used to determine encoding format.
byte Water frequency.
byte Water size.
ore_def[int] An array of ore definitions. The array length is stored as an integer prefix. Factorio doesn’t care what order these are in, but it always alphabetizes during export. Vanilla has six ores: coal, copper-ore, crude-oil, enemy-base, iron-ore, and stone. Unknown ores are ignored and missing ores are set to their defaults.
int Map seed.
int Map width.
int Map height.
byte Starting area size.
boolean Peaceful mode. Enabled if set to 1, disabled otherwise.
byte[*] 0.15.x map string data, if version >= 0.15. This chunk consists of the remainder of the data (minus the checksum)
int CRC32 checksum of all preceding data, as defined by ANSI X3.66 / FIPS 71 / ITU-T V.42 (the same one used by zlib, ethernet, etc.)

0.15 Map Exchange Data

All of the following data values have a special encapsulation format. Preceding each value is a single byte that states whether or not the value is present. If the byte is equal to zero, then the field value is not present. Otherwise, then the field's value follows.

In the LUA structure, this information is stored in the "map_settings" table, which is created by the "map-settings" prototype. Each section in the table below represents a nested sub-table in "map-settings", where the LUA key listed is the key of the table, and all subsequent fields are part of the sub-table. See data/base/prototypes/map-settings.lua for a description of all attributes.

Type LUA key Description
* pollution Pollution
boolean enabled Pollution enabled.
float diffusion_ratio Diffusion ratio.
float min_to_diffuse ???
float ageing Dissipation rate.
float expected_max_per_chunk ???
float min_to_show_per_chunk ???
float min_pollution_to_damage_trees Minimum to damage trees.
float pollution_with_max_forest_damage ???
float pollution_per_tree_damage ???
float pollution_restored_per_tree_damage Absorbed per damaged tree.
float max_pollution_to_restore_trees ???
* steering.default Steering (Default)
float ??? ???
float ??? ???
float separation_force ???
boolean force_unit_fuzzy_goto_behavior ???
* steering.moving Steering (Moving)
float ??? ???
float ??? ???
float separation_force ???
boolean force_unit_fuzzy_goto_behavior ???
* enemy_evolution Evolution
boolean enabled Evolution enabled.
float time_factor Time factor.
float destroy_factor Destroy factor.
float pollution_factor Pollution factor.

Ore_def Ore Definitions

See the page on world generation for more information on frequency, size, and richness.

string Ore name.
byte Ore frequency.
byte Ore size.
byte Ore richness.

Magnitudes (Frequencies / Sizes / Richness)

These are the values used for the frequencies, sizes, and richnesses of ores, water, and the starting area size. None is a valid value for all three options. Anything greater than 5 will crash the game!

0 None / None /None
1 Very Low / Small / Poor
2 Low / Small / Poor
3 Normal / Medium / Regular
4 High / Big / Good
5 Very High / Big / Good