Map exchange string format

This is a technical description of the map exchange string format, used to share map generating configurations with other users. This format is also used to store these settings inside save files for future chunk generation.

Factorio line wraps the entire map exchange string after 57 characters during export (55 code characters + '\r\n', which is fairly standard), 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).

See the page on data types for an explanation of the different types of data used in this document.

Factorio 0.16 and Beyond

Beginning with Factorio 0.16.0, two important changes are made to the encoding of the map exchange string data:

1. The map exchange data inside the Base 64 encoding is further encoded using the zlib compression algorithm. The best way to determine the encoding is to first attempt to parse the map exchange string using zlib, and if that fails, try again using the 0.14+ rules.
2. All numeric data fields longer than 1 byte are encoding using a custom-built variable length integer format described by Factorio developer Rseding at Data_types#Space_Optimized. For appropriate Factorio versions, all such data types (int, short, dict, etc) used in this document represent values encoded using this approach, unless otherwise specifically noted.

After taking these considerations into your codec, proceed using the 0.14+ rules below.

Factorio 0.14 and Beyond

This is the base map exchange string format for all Factorio versions 0.14.x and greater.

Type	Description
short[4]	The version string of Factorio that generated this string, used to determine encoding format. This field is never space optimized.
byte[*]	Map Gen Settings. Variable length. See linked section for information on how to parse.
byte[*]	0.15.x Map Settings. If present, this chunk consists of the remainder of the data (minus the checksum).
uint	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.)

Map Gen Settings

This format matches MapGenSettings.

The "From" column denotes the earliest Factorio version in which that field is present. Most of them are currently labeled as "≤0.14", which means the field was present from at least 0.14. If you have more specific information, please edit this page!

Type	LUA key	From	Description
byte	terrain_segmentation	≤0.14	Water frequency.
byte	water	≤0.14	Water size.
dict<string, byte[3]>	autoplace_controls	≤0.14	An dictionary of Autoplace Controls, with string keys, where the key represents the resource name. Factorio doesn’t care what order this dictionary is in, but it always alphabetizes during export. Vanilla has seven resources: coal, copper-ore, crude-oil, enemy-base, iron-ore, stone, and uranium-ore. Unknown ores are ignored and missing ores are set to their defaults. Factorio 0.16.x adds addition terrain related autoplace features: desert, dirt, grass, sand, trees. With the exception of trees, these resources ignore their richness and as such are not configuration using the map gen GUI, and always have a richness value of 3 ("Regular").
byte[2]	TODO	0.16.0	TODO...
uint	seed	≤0.14	Map seed. This field is never space optimized.
none	shift	≤0.14	This field isn't present in the binary format! But it is part of the Lua structure - by default it's derived from the map seed. I'll slap the algorithm here soon(tm).
uint	width	≤0.14	Map width. This field is never space optimized.
uint	height	≤0.14	Map height. This field is never space optimized.
byte	starting_area	≤0.14	Starting area size.
boolean	peaceful_mode	≤0.14	Peaceful mode. Enabled if set to 1, disabled otherwise.

0.15 Map Settings

All of the following data fields (until noted at the end) 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 "game.map_settings" table, which is created by the "MapSettings" 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 (some of that information has now been copied to this page).

Fields marked with a check (✓) in the "GUI" column are configurable in the new game map generator GUI.

Type	GUI	LUA key	Description
*	✓	pollution	Pollution
boolean	✓	enabled	Pollution enabled.
double	✓	diffusion_ratio	The amount of pollution that is diffused into neighboring chunk per second.
double		min_to_diffuse	This many PUs must be on the chunk to start diffusing.
double	✓	ageing	[Modifier of] the pollution eaten by a chunks tiles.
double		expected_max_per_chunk	Anything bigger than this is visualised as this value.
double		min_to_show_per_chunk	Anything lower than this (but > 0) is visualised as this value.
double	✓	min_pollution_to_damage_trees	Any pollution above this amount starts to damage trees.
double		pollution_with_max_forest_damage	???
double		pollution_per_tree_damage	???
double	✓	pollution_restored_per_tree_damage	The amount of pollution absorbed by a tree when it is damaged by pollution.
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.
double	✓	time_factor	Percent increase in the evolve factor for every second.
double	✓	destroy_factor	Percent increase in the evolve factor for every destroyed spawner.
double	✓	pollution_factor	Percent increase in the evolve factor for every 1000 PU [produced].
*	✓	enemy_expansion	Enemy Expansion
boolean	✓	enabled	Enemy expansion enabled.
int	✓	max_expansion_distance	Distance in chunks from the furthest base around.
int		friendly_base_influence_radius	???
int		enemy_building_influence_radius	???
double		building_coefficient	Expansion algorithm. See LUA file for details.
double		other_base_coefficient
double		neighbouring_chunk_coefficient
double		neighbouring_base_chunk_coefficient
double		max_colliding_tiles_coefficient	A chunk has to have at most this much percent unbuildable tiles for it to be considered a candidate.
int	✓	settler_group_min_size	Size of the group that goes to build new base (in game this is multiplied by the evolution factor).
int	✓	settler_group_max_size
int	✓	min_expansion_cooldown	Minimum cooldown.
int	✓	max_expansion_cooldown	Maximum cooldown.
*		unit_group	Unit Group
int		min_group_gathering_time	A pollution triggered group's waiting time is a random time between min and max gathering time.
int		max_group_gathering_time
int		max_wait_time_for_late_members	After the gathering is finished the group can still wait for late members, but it doesn't accept new ones anymore.
double		max_group_radius	Limits for group radius.
double		min_group_radius
double		max_member_speedup_when_behind	When a member falls behind the group he can speedup up till this much of his regular speed.
double		max_member_slowdown_when_ahead	When a member gets ahead of its group, it will slow down to at most this factor of its speed.
double		max_group_slowdown_factor	When members of a group are behind, the entire group will slow down to at most this factor of its max speed.
double		max_group_member_fallback_factor	If a member falls behind more than this times the group radius, the group will slow down to max_group_slowdown_factor.
double		member_disown_distance	If a member falls behind more than this time the group radius, it will be removed from the group.
int		tick_tolerance_when_member_arrives	???
int		max_gathering_unit_groups	Maximum number of automatically created unit groups gathering for attack at any time.
int		max_unit_group_size	Maximum size of an attack unit group. This only affects automatically-created unit groups.
*		path_finder	Path Finder
uint		fwd2bwd_ratio	The pathfinder performs a step of the backward search every fwd2bwd_ratio'th step. The minimum allowed value is 2, which means symmetric search.
double		goal_pressure_ratio	When comparing nodes in open which one to check next, heuristic value is multiplied by this ratio. The higher the number the more is the search directed directly towards the goal.
boolean		use_path_cache	???
double		max_steps_worked_per_tick	When this is exhausted no more requests are allowed. At the moment the first path to exhaust this will be finished (even if it is hundreds of steps).
int		short_cache_size	Number of elements in the cache.
int		long_cache_size
double		short_cache_min_cacheable_distance	Minimal distance to goal for path to be searched in short path cache.
int		short_cache_min_algo_steps_to_cache	Minimal number of algorithm steps for path to be inserted into the short path cache.
double		long_cache_min_cacheable_distance	Minimal distance to goal for path to be searched in long path cache.
int		cache_max_connect_to_cache_steps_multiplier	When searching for connection to path cache path, search at most for this number of steps times the initial estimate.
double		cache_accept_path_start_distance_ratio	When looking for path from cache make sure it doesn't start too far from requested start in relative distance terms.
double		cache_accept_path_end_distance_ratio	When looking for path from cache make sure it doesn't end too far from requested end. This is typically higher than accept value for the start because the end target can be moving.
double		negative_cache_accept_path_start_distance_ratio	Same as cache_accept_path_start_distance_ratio, but used for negative cache queries.
double		negative_cache_accept_path_end_distance_ratio	Same as cache_accept_path_end_distance_ratio, but used for negative cache queries.
double		cache_path_start_distance_rating_multiplier	When assigning rating to the best path this * start distances is considered.
double		cache_path_end_distance_rating_multiplier	When assigning rating to the best path this * end distances is considered. This is typically higher than value for the start to achieve better path end quality.
double		stale_enemy_with_same_destination_collision_penalty	Somewhere along the path is stuck enemy we need to avoid. This is mainly to handle situations when units have arrived and are attacking the target, then units further in the back will use this and run around the target.
double		ignore_moving_enemy_collision_distance	If there is a moving unit further than this we don't really care.
double		enemy_with_different_destination_collision_penalty	Enemy is not moving/or is too close and has different destination.
double		general_entity_collision_penalty	Simplification for now - collision with everything else is this.
double		general_entity_subsequent_collision_penalty	Collision penalty for successors of positions that require destroy to reach.
int		max_clients_to_accept_any_new_request	Uptil this amount any client will be served by the path finder (no estimate on the path length).
int		max_clients_to_accept_short_new_request	From max_clients_to_accept_any_new_request till this one only those that have a short estimate will be served.
int		direct_distance_to_consider_short_request	This is the "threshold" to decide what is short and what is not.
int		short_request_max_steps	If a short request takes more than this many steps, it will be rescheduled as a long request.
double		short_request_ratio	How many steps will be allocated to short requests each tick, as a ratio of all available steps per tick.
int		min_steps_to_check_path_find_termination	Absolute minimum of steps that will be performed for every path find request no matter what.
double		start_to_goal_cost_multiplier_to_terminate_path_find	If the amount of steps is higher than this times estimate of start to goal then path finding is terminated.
Note: The following fields do not use the special encapsulation method.
byte[4]		. (root)	Other
int		max_failed_behavior_count	If a behavior fails this many times, the enemy (or enemy group) is destroyed. This solves biters stuck within their own base.
Type	GUI	LUA key	Description

Difficulty Settings

This information is instead stored in the LUA structure at game.difficulty_settings, which is prototyped by DifficultySettings. These fields do not use the special encapsulation method noted above.

Type	GUI	LUA key	Description
byte[10]	✓	difficulty_settings	Difficulty Settings
byte	✓	recipe_difficulty	Recipe difficulty. 0 for Normal, 1 for Expensive.
byte	✓	technology_difficulty	Technology difficulty. 0 for Normal, 1 for Expensive.
double	✓	technology_price_multiplier	Technology price multiplier.

Note: these values are typically defined using the constants at defines.difficulty_settings.

Autoplace Control

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

Type	LUA key	Description
byte	frequency	Ore frequency.
byte	size	Ore size.
byte	richness	Ore richness.

Map Gen Size

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.

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

Each of the values in a triplet (such as "low", "small", and "poor") are synonymous.