The binary format for Fallout 4 PC save files.

Fallout 4 Save File Format.md

Fallout 4 Save File Format

The binary format for Fallout 4 PC save files. This document was created by reverse-engineering files from version 1.2.37.0 of the game.

Note: This document is incomplete!

Table of Contents

• Table of Contents
• Format
  • Header
• Types

Format

Field Name	Type	Remarks
Magic ID	char[12]	Always FO4_SAVEGAME
Header Size	uint32	The total size (in bytes) of the header
Header	header	See: Header
Snapshot	uint8[Width * Height * 4]	An array containing raw pixel data for the thumbnail. The array is stored as 32-bits-per-pixel ARGB.
Format Version	uint8	The save file format version (?). Current value is 61
Game Version	wstring	The game's patch version when the save was created in dot-notation (ex 1.2.37.0)
Plugin Info Size	uint32	The total size (in bytes) of the plugin information
Plugins Count	uint8	The number of plugins used by this save
Plugins	wstring[Plugins Count]	Each string is a file name for a .esm or .esp file in the Data directory.

Header

Field Name	Type	Remarks
Engine Version	uint32	The version of Creation Engine that created this file (?). Current value is 11
Save Number	uint32	Incremented by 1 each time a game is saved
Character Name	wstring
Character Level	uint32
Character Location	wstring	Name of the player's current location
Play Time	wstring	The amount of time played. Stored as xd.yh.zm.x days.y hours.z minutes where x, y, and z are any arbitrary integers. An example of for a character that has played 2 days, 2 hours, and 3 minutes would be 2d.2h.3m.2 days.2 hours.3 minutes
Character Race	wstring	The internal editor ID of the player's race. Probably always HumanRace
Character Sex	uint16	The sex (gender) of the player character. 0 = male, 1 = female
Current Character Experience	float32	The current amount of experience the player has attained for progressing to the next level
Required Experience	float32	The amount of experience needed to progress to the next level
Filetime	FILETIME	The real-world time the save file was created
Snapshot Width	uint32	The width (in pixels) of the save thumbnail
Snapshot Height	uint32	The height (in pixels) of the save thumbnail

Types

Type Name	Size (in bytes)	Remarks
char	1	An 8-bit character
wstring	Variable	A wstring is a string prefixed with a uint16 denoting the length, followed by exactly that many characters
uint8	1	An unsigned 8-bit integer
uint16	2	An unsigned 16-bit integer
uint32	4	An unsigned 32-bit integer
float32	4	A single-precision, 32-bit, floating-point number
FILETIME	8	See: https://msdn.microsoft.com/en-us/library/windows/desktop/ms724284(v=vs.85).aspx

Awww, that's a real bummer, because Fo4 Multiplayer would be a blast!
I mean I'm not OP, I didn't knew.

If anyone wonder, with version 1.10.984.0, plugins are divided in two sections. The first one, as described is followed by another plugin2 count (uint32) and wstring[Plugins2 Count] that store mods and creation kit enabled.