The file is read with FileReader and handed straight to the emulator core. It is never uploaded. There is no server side here — the page refuses any network request that is not to its own origin, and its content-security-policy makes the browser refuse one too.
Battery saves (the in-game SAVE) persist in this browser's IndexedDB, keyed per game, and survive reload. Clearing site data clears them.
No ROM, and nothing extracted from one, ships with this page.
←↑↓→ D-pad · X A · Z B ·
Enter Start · Shift Select · gamepads and on-screen buttons work too