Subnautica’s save unit is a slot directory. Each slot contains several records describing world and player state, which means a backup made from one selected file can be incomplete. The safest procedure is to close the game and copy the entire `SavedGames` directory or the complete slot you care about. Storefront matters because the base path can change—particularly between the standard game directory and the Epic LocalLow location.
Known Subnautica save-file structure
The researched filename or folder pattern is slot0000, slot0001, … save directories. File-extension context: .bin, .json The documented format notes are: Subnautica uses slot directories rather than one portable save file. A slot contains multiple binary/metadata records, so preserving the full slot folder is safer than selecting one .bin file.
Why an extension is not enough
A save filename can identify a likely container, but it does not prove the internal schema, game version, checksum rules, encryption state, or editability. A slot folder is a coordinated set of files. Mixing parts from different slot revisions can create a state that was never produced by the game. SaveEditor therefore separates file identification from Tool compatibility and only labels a game-specific Tool Verified when its exact profile/version evidence passes the runtime gate.
Where the format is stored
PC save locations: Windows: Standard Windows: <path-to-game>SNAppDataSavedGames
Epic: %USERPROFILE%AppDataLocalLowUnknown WorldsSubnauticaSubnauticaSavedGames | macOS: $HOME/Library/Application Support/unity.Unknown Worlds.Subnautica/Subnautica/SavedGames | Linux / Steam Play: Steam Play: <SteamLibrary-folder>/steamapps/compatdata/264710/pfx/. Storefront context: Steam, Epic Games Launcher, Microsoft Store / Xbox app. PCGamingWiki documents different Windows locations for standard installs and Epic. Microsoft Store packaging should be treated separately when the standard SNAppData path is absent. This matters because two releases can use different containers or companion files even when the visible slot name is similar.
Back up before inspecting or editing
Copy complete slot directories or the entire SavedGames folder. Do not back up only the most obvious binary file inside a slot. A read-only viewer is lower risk than a writer, but the live save should still be copied first. Cloud context also matters: Cloud support depends on storefront. The local slot directory should still be backed up before game updates, mods, or migration. Keep the original bytes available so any experiment can be reversed without relying on a cloud service or automatic backup.
What this reference does not claim
This page does not infer an undocumented checksum algorithm, encryption key, compression layer, or cross-store conversion from the file extension. Troubleshooting evidence: If the expected SNAppData directory is empty, identify the storefront and check the documented Epic LocalLow path. Keep older slot copies intact while diagnosing. Those questions require a verified parser/profile or a game-specific source, not a generic format guess.
Verification context: Standard Windows, Epic, macOS, and Steam Play locations were reviewed against current PCGamingWiki coverage.