GenX-DOS is a static site with no backend — no accounts, no cookies, no analytics, and nothing you do is ever sent anywhere. A few things, though, are written to your browser's own semi-permanent storage (localStorage / IndexedDB) so they survive a reload or a return visit. This page is the complete list of what those are and when they're written.
| Data | Where it's stored | When it's written | Which bundles |
|---|---|---|---|
| Save-state slots — five per game; an instant snapshot of the running machine | IndexedDB — database gx-savestate, store slots, keyed platform:game:slot |
Manually — only when you click a Save slot | Any bundle showing the Save / Load buttons: the EmulatorJS cores via genx-savestate.js, and the standalone engines that expose a reachable state API via genx-savestate-std.js |
| Model 100 battery-backed RAM — the 32 KB base RAM behind the Startup Menu (your TEXT / ADRS / SCHEDL data and files) | localStorage — key genx-m100-ram (base64) |
Automatically — every 10 seconds and on tab close; bare-boot Model 100 only (loaded games stay ephemeral) | Tandy TRS-80 Model 100 (m100) |
| In-game cartridge saves — a game's own SRAM / battery save (e.g. Phantasy Star) | IndexedDB — EmulatorJS's IDBFS save database (synced with syncfs) |
Automatically — when the game itself writes its save RAM | EmulatorJS bundles (handled by the bundled engine) |
| Emulator settings — control mappings, volume, video / shader options | localStorage — ejs-settings… |
Automatically — when you change a setting in the EmulatorJS menu | EmulatorJS bundles (handled by the bundled engine) |
| Arcade input config — one 20-byte file that puts Hang-On's brake on a pad axis, which the emulator reads at startup | IndexedDB — the same EmulatorJS save database, at MAME 2003-Plus/mame2003-plus/cfg/default.cfg |
Automatically — written at boot, on the Hang-On cabinet only | Arcade (arcade) |
The first two rows and the last are GenX-DOS's own code (genx-savestate.js / genx-savestate-std.js, the Model 100 page wrapper, and genx-ejs-boot.js for the arcade config); the middle two are the bundled EmulatorJS engine doing what it normally does. Save-state slots — the first row — can be exported to a file and restored; see below.
What isn't stored
No cookies, no login, no personal data, no telemetry — the site has no server to send any of it to. Everything in the table lives only in your browser, scoped to the GenX-DOS origin, and never leaves your machine.
Backing up your saves — and moving them between addresses
Any bundle with the Save / Load buttons also has a backup button beside them, holding two things:
- export all saves — writes every save-state slot on the whole site (not just the game you're looking at) to a single
genx-dos-saves-YYYY-MM-DD.jsonfile. The count in brackets tells you how many slots that is before you click. - restore from file — reads one of those files back.
Restoring is not destructive. If a slot already holds a save, the one in the file is skipped rather than written over, so restoring an old backup can never overwrite newer progress. The button reports what happened — restored 12, kept 3 means twelve slots were empty and filled, and three already had something in them and were left alone. If you want the file's version, delete or overwrite that slot first.
Why this matters if the address changes
Browsers scope storage to the origin — the exact address in the bar. IndexedDB cannot be read across origins by design, so saves made at one address are simply not visible from another. They aren't deleted; they're unreachable, and they stay that way.
So if you've been playing at one address and the site moves to another, export before you switch and restore afterwards, or your slots stay behind at the old one. (The old address keeps working for as long as it exists, so there's no rush — but nothing carries across on its own.)
Clearing it
All of it is wiped by your browser's "clear site data" (or by clearing history / cookies + site data) for the GenX-DOS origin. Clearing it removes your save-state slots, Model 100 memory, in-game cartridge saves, emulator settings and the arcade input config — there is no copy anywhere else, so use backup → export all saves first if you want to keep them.
See also the Save / load state section of the Project Overview, and the repository's SECURITY.md.