Persona 3 Reload has unusually useful public Steam Cloud metadata: SteamDB shows the exact WinAppDataRoaming root and SaveData*.sav pattern. That makes the Steam backup boundary clear, but it does not solve Microsoft Store compatibility because the Game Pass version lives in WGS and community transfer workflows use conversion/encryption-aware tools. SaveEditor therefore documents both locations while explicitly separating “where the file is” from “whether it is directly compatible.” A safe migration starts with a complete backup of both source and target directories.
Known Persona 3 Reload save-file structure
The researched filename or folder pattern is Steam: SaveData*.sav; Microsoft Store: opaque WGS files/containers.. File-extension context: .sav The documented format notes are: Steam cloud configuration explicitly maps WinAppDataRoaming/SEGA/P3R/Steam/{64BitSteamID} with a SaveData*.sav pattern. Microsoft Store uses WGS and transfer to Steam may require format/encryption-aware tooling.
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. Game Pass-to-Steam migration can require encryption/container conversion. The existence of both files on disk does not make them byte-compatible. 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: Steam: %APPDATA%SEGAP3RSteam<64-bit-SteamID> ; Microsoft Store: %LOCALAPPDATA%PackagesSEGAofAmericaInc.L0cb6b3aea_s751p9cej88mtSystemAppDatawgs<user-id>. Storefront context: Steam, Microsoft Store. The Steam and Microsoft Store save containers are not equivalent. Do not rename an arbitrary WGS file to SaveData001.sav and assume it is valid. 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 the complete Steam-ID directory or the complete Microsoft WGS tree before any transfer. Keep original SaveData files untouched until the migrated save has been loaded and re-saved successfully. A read-only viewer is lower risk than a writer, but the live save should still be copied first. Cloud context also matters: Steam Cloud and Xbox Cloud are documented. SteamDB reports a 550 MiB cloud quota and the SaveData*.sav pattern for Steam. 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 Steam does not show an imported slot, confirm the 64-bit Steam ID folder and SaveData numbering. For Microsoft Store migration, restore the original WGS copy if a conversion tool fails. Those questions require a verified parser/profile or a game-specific source, not a generic format guess.
Verification context: Reviewed against PCGamingWiki Persona 3 Reload and current SteamDB user-file-system mapping for app 2161700.