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.
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.
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).
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.
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.
<file>
: Starfield save file to parse (.sfs
)
-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
-
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 toC:\Test\MySave.json
-
StarfieldSaveTool C:\Test\MySave.sfs --output-json-file --output-raw-file
will output metadata to the console and toC:\Test\MySave.json
and save the decompressed data chunks from the.sfs
file toC:\Test\MySave.raw
See Example.json for a complete JSON export.
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.
Name | Type | Description |
---|---|---|
magic | char[12] |
Magic bytes "SFS_SAVEGAME" |
headerSize | uint |
Size of header |
header | HEADER | Header data block |
saveVersion | byte |
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.
Name | Type | Description |
---|---|---|
engineVersion | uint |
Engine version? This is 27 , Fallout 4 was 11 . |
saveVersion | byte |
Save file format version. Currently 122 |
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
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 |
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.
Name | Type | Description |
---|---|---|
pluginNameSize | ushort |
Size of plugin name |
pluginName | string |
Plugin name |
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 |