# Saving | Big Mech Energy Idle Wiki

The game **autosaves to this browser every 15 seconds** (localStorage). Nothing leaves your machine: there is no account, no server, no sync. That also means browser storage is the only copy, and browsers may evict it without asking. The **save code** is the real backup.

- **Export:** Settings → Save → Export copies a code to your clipboard. Paste it anywhere safe (a note, a file). It restores everything: progress, parts, pets, the works.
- **Import:** paste any code into Settings → Save → Import. Codes from older versions of the game always load (saves migrate forward automatically); codes from a NEWER version than the build you are running are refused rather than guessed at.
- **Offline progress** accrues while the tab is closed, up to a cap, and is reported when you return.
- The yellow banner that appears when you have no recent backup does exactly one thing: it copies a fresh save code to your clipboard. Audio settings are device-local and deliberately not part of the save.

#### The save code format (for fan tools)

Codes are deliberately parseable. The recipe, should you want to build a planner, editor or analyzer:

- A code is the string `BME1-` followed by **LZString compressToBase64** output (the `lz-string` library, any port works).
- Decompressing yields JSON: `{ version, savedAt, data }`. `version` is the save schema version, `savedAt` a Unix ms timestamp, `data` the full game state.
- Inside `data`, every big number (Scrap, Components, HP...) is a **Decimal string** like `"1.5e21"`, not a JSON number. Parts, wires, pets, minigame states are plain objects; the authoritative shape is `src/core/save/schema.ts` in the repo.
- To produce a code the game will accept: build the same JSON envelope, compress with `compressToBase64`, prepend `BME1-`. Imports are validated strictly and migrated by `version`, so older shapes stay loadable forever.
- Fair warning for tool authors: the schema can change between updates while the game is in active development. The `version` field is your compatibility signal.