NotAlterra

Subnautica 2 Save Manager, Windows Native GUI

NotAlterra is an unofficial tool for managing Subnautica 2 save files. It locates your save folders, backs up and restores .sav / .bak files, and lets you inspect the internal metadata of every save.

Not affiliated with Unknown Worlds Entertainment or KRAFTON.

Features

• Manual path entry — set your save folder from the menu
• Recover a corrupted .sav from its .bak backup with rollback
• Create / restore full backups (only savegame_* files)
• Manage UE5 Config .ini files — backup, restore, delete
• Inspect any .sav or .bak file — full GVAS metadata dump
• Slot grouping with Multiplayer / Single Player detection
• Playtime extraction — displays total playtime from save metadata
• Warns on name changes and mode switches before recovery

⚠ Important

NotAlterra is a read-only metadata inspector and backup tool. It does not edit .sav files in-place. Recovery operations restore a .bak copy to .sav (identical to a manual file copy). No save data is ever patched, rewritten, or modified byte-by-byte.

Metadata extraction uses a heuristic byte-scan — it searches for known property names (DisplayName, GameMode, PlaytimeSeconds, etc.) as raw byte patterns in the binary GVAS data. This is NOT a full UE5 GVAS structure walker. Some fields may be absent or misidentified if the save format changes in a game update.

Installation

Download the latest installer: NotAlterra-Windows-x64.exe

Installer	Size	Dependencies
NotAlterra-*-x64.exe	~19 MB	.NET 9 runtime + Windows App SDK 1.8

Downloads and installs both .NET 9 Desktop Runtime and Windows App SDK 1.8 if missing. Safe to re-run. A desktop shortcut is optional.

Where Files Live

%LOCALAPPDATA%\Subnautica2\Saved\SaveGames\
    savegame_0.sav
    savegame_0.bak
    savegame_0_1.bak
    savegame_1.sav
    ...

Privacy

NotAlterra makes no network connections. No telemetry. No data leaves your machine.

• The application never calls home, there are no update checks, no analytics, no crash reporters.
• It runs entirely offline. Your save files and their metadata stay on your machine.
• The Windows App SDK runtime has opt-in telemetry which NotAlterra does not enable.
• Configuration is stored in HKCU\Software\NotAlterra registry keys, no config files on disk.

If network features are added in a future version, they will require explicit user opt-in.

Safety

• Installer requires admin (writes to Program Files). The app itself runs without elevation.
• No network connections
• Read-only inspect mode won't touch files
• Pre-restore snapshots created automatically
• UE5 .ini file delete requires a prior backup

Backup Format

Backups are stored as tar.gz archives: one archive per backup event, containing all savegame_* files. Standard tar -xzf recovers data without the tool (no vendor lock-in). Each archive contains a MANIFEST file with SHA256 hashes of every backed-up file for integrity verification.

Credits

• Sidebar background video by Pachon in Motion, @Pachon.In.Motion, Provincia de Buenos Aires, Argentina

License

MIT — see LICENSE.md.