Map exchange string format

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