For New Vegas, the save file is only part of a reproducible modded setup. Back up the entire Saves folder and separately record the active mod list before changing load order or moving progress to another PC.
For this PC reference, the documented storage is Windows: %USERPROFILE%DocumentsMy GamesFalloutNVSaves. The known file or folder pattern is *.fos save files plus paired metadata/backup artifacts when present. New Vegas uses Bethesda Gamebryo save records with the .fos extension. Mods, DLC, load order, and script state can be embedded in progress, so a byte-level file match does not guarantee a safe modded restore.
Backup guidance: Close Fallout: New Vegas, let the launcher finish any synchronization, then copy the complete documented save directory to a dated folder outside the live path. Preserve companion files rather than selecting only the newest-looking record. Cloud support differs by storefront; keep an offline copy of the Saves folder and the mod/load-order context for modded games. Launcher and cloud context matters because The active Steam, GOG, Epic Games Store, Microsoft Store installation determines which local profile and cloud copy can overwrite the save. Identify the storefront and account before restoring files.
Compatibility and recovery should stay conservative. Treat saves as version-, storefront-, account-, and mod-sensitive unless the game or a separately verified migration workflow proves otherwise. A similar filename or extension is not evidence that two releases are interchangeable. If the expected progress is not visible, If progress is missing after a restore, confirm the active Windows account, storefront/profile, cloud state, and exact directory first. Restore the untouched backup before experimenting with individual files or older autosaves. SaveEditor.com only labels a game-specific editor as available when a separate linked Tool has a verified operational runtime; this reference page by itself is not an editor claim.