StarfieldSaveTool

A tool to decompress and convert Starfield save games to JSON format. Save games are stored in a compressed format (.sfs) and this tool will decompress the data and output the metadata to JSON. Save games are normally found in the C:\Users\<USERNAME>\Documents\My Games\Starfield\Saves directory.

This was primarily developed as part of the Starfield extension for Vortex, the mod manager created by Nexus Mods.

Any help with the file format would be appreciated, the majority of unknowns are in the header of the compressed sfs file, and the plugins data within the decompressed file. I'm not including the main data blocks of the decompressed file as we are primarily interested in the metadata.

Thanks to Mod Organizer 2 for it's help to get started writing this tool and to help formalize this file format research. Special thanks to Silarn for the reverse engineering help.

Contribute

This is all work in progress and there is plenty more with this file format that needs reverse engineering and explaining. All help is welcome and here are some tools that might help:

• Template files for .sfs (compressed) and .sfs (decompressed) that can be used in 010 Editor.

Usage

The tool will always output JSON to the console. See below for options to write JSON to a file and to write the decompressed data to a file (useful for reverse engineering).

Drag-and-drop

The simplest way to use the tool is to drag-and-drop a save file (.sfs) onto the Launch.bat file. This uses the --output-json-file and --output-raw-file options below.

Command Line

StarfieldSaveTool <file> [options]

As the tool always outputs JSON to the console, you can use this tool via another program to parse the JSON output.

Arguments

<file>: Starfield save file to parse (.sfs)

Options

  -j, --output-json-file  Write JSON output to file [default: False]
  -r, --output-raw-file   Write raw output to file [default: False]
  -c, --change-file       Experimental: Writes the modified save file [default: False]
  --version               Show version information
  -?, -h, --help          Show help and usage information

Usage Examples

• StarfieldSaveTool C:\Test\MySave.sfs will output metadata only to the console

• StarfieldSaveTool C:\Test\MySave.sfs --output-json-file will output metadata to the console and to C:\Test\MySave.json

• StarfieldSaveTool C:\Test\MySave.sfs --output-json-file --output-raw-file will output metadata to the console and to C:\Test\MySave.json and save the decompressed data chunks from the .sfs file to C:\Test\MySave.raw

Example JSON

See Example.json for a complete JSON export.

Starfield Save file (.SFS)

The .sfs file is a compressed file format used by Starfield. The file format is a series of compressed data chunks in the Zlib format. The data chunks are compressed using the Deflate algorithm using Fast Compression. Here is a work-in-progress breakdown of the binary file format.

Name	Type	Description
magic	char[4]	Magic bytes "BCPS"
version0	uint	Version number
chunkSizesOffset	uint64	Position where the compressedChunkSizes array begins
unknown0	uint64
compressedDataOffset	uint64	Position where the compressed chunks begins
uncompressedDataSize	uint64	Size of uncompressed save file
version1	float	Different version number?
unknown1	uint
sizeUncompressedChunks	uint64	Size of each uncompressed chunk
paddingSize	uint64	Determines start of each compressed chunk. Chunks are padded out to the nearest 16 bytes
unknown2	uint
compressionType	char[4]	"ZIP ". Might have other compression types? Denotes start of compressed chunks
compressedChunkSizes	uint[]	Array of compressed sizes for each chunk
compressedChunks	chunk[]	The size of each chunk is determined by the compressedChunkSizes array and is padded to the nearest 16 bytes.

Below is the file that is decompressed from the compressed chunks in the .sfs save file as described above.

Dat file (Decompressed Starfield Save file)

Name	Type	Description
magic	char[12]	Magic bytes "SFS_SAVEGAME"
headerSize	uint	Size of header
header	HEADER	Header data block
saveVersion	ubyte	Save file format version. Currently 122
currentGameVersionSize	ushort	Size of the current game version string
currentGameVersion	string	Current game version string
createdGameVersionSize	ushort	Size of the created game version string
createdGameVersion	string	Created game version string
pluginInfoSize	ushort	Size of the plugin information data
pluginInfo	PLUGIN_INFO	Plugin information data block

Rest of file has not been worked out yet.

HEADER

Name	Type	Description
engineVersion	uint	Engine version? This is 27, Fallout 4 was 11.
saveVersion	byte	Save file format version. Currently 143
saveNumber	uint	Incremented by 1 each time overwritten
playerNameSize	ushort	Size of player name string
playerName	string	Player Name. Not used in game, only used for load screen?
playerLevel	uint	Player Level
playerLocationSize	ushort	Size of Player Location string
playerLocation	string	Player Location
playtimeSize	ushort	Size of Playtime string
playtime	string	Playtime. xd.yh.zm.x days.y hours.z minutes where x=days, y=hours and z=minutes
raceNameSize	ushort	Size of Race Name string
raceName	string	Race Name
gender	ushort	Gender. 0=Male, 1=, 2=
experience	float	Player's experience
experienceRequired	float	Experience required for next level
time	FILETIME	Last played timestamp.
padding	byte[8]	Unknown
unknown	uint	Unknown

What follows the INFO block is the PLUGIN_INFO block

PLUGIN_INFO

Name	Type	Description
unknown0	byte
unknown1	byte
pluginCount	byte
plugins	PLUGIN[]	Array of plugin data
lightPluginCount	byte
lightPlugins	PLUGIN[]	Array of plugin data

Medium plugins were added in save file version 122. They are stored after the light plugins if saveVersion >= 122

Name	Type	Description
mediumPluginCount	byte
mediumPlugins	PLUGIN[]	Array of plugin data

PLUGIN

There are different types of Plugin data blocks.

• Native game plugins only contain the pluginName
• Non-native plugins (if SaveVersion >= 122) contain extra data, including Creation information and flags where appropriate. If an older SaveVersion, the extra data is not present.
• If SaveVersion >= 140, there is an extra byte to indicate if there is extra data for the plugin.

Name	Type	Description	Comment
pluginNameSize	ushort	Size of plugin name
pluginName	string	Plugin name
extraInfo	ubyte	0=no, 1=yes	Only exists if SaveVersion >= 140

Extra Data

Name	Type	Description
creationNameSize	ushort	Size of Creation Name string. 0 if not a Creation.
creationName	string	Creation Name string
creationIdSize	ushort	Size of Creation ID. 0 if not a Creation.
creationId	string	Creation ID. GUID that matches xyz
flagsSize	ushort	Size of flags data. Sometimes 0.
flags	byte[flagsSize]	Unknown data structure
achievementCompatible	byte	0=no, 1=yes