Save file ZIP structure

Top-level file layout of a Stationeers save ZIP. The archive is a standard ZIP; each entry is plaintext XML, binary voxel data, or a PNG. Sizes in the example column are from an observed mid-sized save and are indicative, not exact.

File table

File	Size (example)	Content
world_meta.xml	~700 B	Save metadata: world name, version, stats
world.xml	~2.6 MB	ALL game data: things, atmospheres, networks, players
terrain.dat	~184 KB	Terrain/voxel data (binary)
preview.png	~125 KB	Save thumbnail
screenshot.png	~139 KB	Screenshot

The five names are code constants (SaveLoadConstants, 0.2.6403.27689 decompile lines 265202-265210): TerrainFileName = "terrain.dat", MetaFileName = "world_meta.xml", WorldFileName = "world.xml", PreviewFileName = "preview.png", ScreenshotFileName = "screenshot.png". The writer (SaveHelper.Save, line 264972) emits them in the order world_meta.xml, world.xml, terrain.dat, preview.png, screenshot.png, and skips the two PNGs entirely in batch mode (if (!GameManager.IsBatchMode), line 265020), so a save written BY a dedicated server has only the first three members. A save that carries the PNGs was last written by a client.

Mod sidecar entries

A save ZIP can carry additional entries beyond the five standard members: mods append their own files at save time. Observed entry listing of a real modded save (DedicatedServer/data/saves/Luna/Luna.save, 2026-07-02, sizes in bytes):

       698  world_meta.xml
  61514025  world.xml
    456908  terrain.dat
    149788  preview.png
    177904  screenshot.png
       779  equipmentplus-active-slots.xml
       551  equipmentplus-beam.xml
      3667  pwrxmplus-autoaim.xml
      4421  pwrgridplus-passthrough.xml
       486  pwrgridplus-priority.xml

The last five are per-mod sidecars written by this repository's mods: equipmentplus-active-slots.xml and equipmentplus-beam.xml by EquipmentPlus (ActiveSlotSideCar.SideCarEntryName, HelmetBeamSideCar.SideCarEntryName), pwrxmplus-autoaim.xml by PowerTransmitterPlus (AutoAimSideCar.SideCarEntryName), and pwrgridplus-passthrough.xml / pwrgridplus-priority.xml by PowerGridPlus (PassthroughSideCar.SideCarEntryName, PrioritySideCar.SideCarEntryName). The mechanism, and why it works, is documented in ../GameSystems/SaveZipExtension.md: the game's LOAD path looks up known entry names and silently ignores everything else, while the game's SAVE path rebuilds the ZIP from scratch with only the known members, so a mod must re-append its sidecar on every save (Harmony patch on the private SaveHelper.Save worker).

Consequences for offline save tooling:

• Any tool that repacks a save ZIP MUST copy through unknown entries verbatim (name, order, bytes), or it silently strips mod data. A repack that hardcodes the five standard members destroys the sidecars without any error; the mods then see missing state on next load. This bit in practice on 2026-07-02: tools/save-edit/stationeers_save.py repack() writes only the five standard members, so the save-surgery session used a one-off script that copies every entry through and edits only world.xml, precisely to keep the five sidecars alive.
• The sidecar names are chosen by each mod; there is no registry and no namespace rule beyond collision avoidance. Treat "entries I do not recognize" as load-bearing mod data, never as junk.

Verification history

• 2026-04-20: page created from the Research migration. Source: F0220 (save file ZIP structure).
• 2026-07-02: re-confirmed the file table against the 0.2.6403.27689 decompile (SaveLoadConstants names, SaveHelper.Save write order, batch-mode PNG skip) and added the "Mod sidecar entries" section from the observed Luna.save entry listing during the same day's save-surgery session. Mechanism cross-referenced to ../GameSystems/SaveZipExtension.md rather than duplicated.

Open questions

None at creation.