Sonic the Hedgehog
UntestedMega Drive · 1991 · Platformer · Decompilation
The one that started it: Green Hill to Scrap Brain, at speed.
Controls
| Arrow keys | D-pad |
| Z / X / C | A / B / C (any of them jumps) |
| Enter | Start |
| Gamepad | any standard controller, detected automatically (untested) |
| Touch | EmulatorJS on-screen Mega Drive pad on phones and tablets (untested) |
About this build
Sonic the Hedgehog built from the sonicretro/s1disasm disassembly. The build is byte-identical to a retail REV00 (USA, Europe) cartridge — sha1 6ddb7de1e17e7f6cdb88927bd906352030daa194 — and runs in the browser on a WebAssembly build of genesis_plus_gx. You supply your own ROM: it is read in your browser with the File API, SHA-1'd against the revisions the disassembly documents, and handed straight to the emulator. The page blocks every cross-origin request before the emulator loads, so your file cannot leave the tab.
- Built from
- the sonicretro/s1disasm disassembly, assembled with AS to a matching ROM and run on EmulatorJS (genesis_plus_gx, WebAssembly)
- Type
- Decompilation
- Game files
- Your own Sonic the Hedgehog ROM, No-Intro '(USA, Europe)' REV00, sha1 6ddb7de1e17e7f6cdb88927bd906352030daa194. REV01 is recognised and runs, and the disassembly reproduces it too with Revision = 1. Nothing is uploaded.
- Code licence
- sonicretro/s1disasm; EmulatorJS GPL-3.0; genesis_plus_gx core (Genesis Plus GX licence, NON-COMMERCIAL — redistributions may not be sold or used in a commercial product or activity)
- Assets
- None distributed — the player supplies their own ROM
- Source
- sonicretro/s1disasm ↗
What has been tested
Byte-exact reassembly (cmp against the staged ROM: 0 differing bytes; upstream chkbitperfect reports bit-perfect REV00). In the browser, audio muted throughout: the ROM is read from a real <input type=file> with a matching sha1, zero off-origin and zero uploading requests observed at the CDP network layer, canvas asserted non-zero, and Green Hill Zone Act 1 cleared at 59.8 fps — confirmed from the game's own work RAM (v_gamemode 0x0C, f_demo 0, v_act 0 -> 1), not from a screenshot, because Sonic 1's attract demo is screenshot-identical to play.
Last tested 2026-10-05 in Chrome 151 (headless, software GL). Full playthrough: not verified. How games are tested.
Known limitations
- Not hosted: both available Mega Drive WebAssembly cores carry a non-commercial clause, and no OSI-clean alternative exists.
- Not yet playable here: no hosted page has been published for this title.
- Requires your own ROM; none is provided.
- Audio starts muted; unmute from the emulator's volume control.
- The only Mega Drive cores available to this stack (genesis_plus_gx, picodrive) are non-commercial-licensed, which blocks hosting under the current policy.
- Verified as far as clearing Green Hill Zone Act 1 under automation; later zones, bosses and special stages have not been play-tested.
Saves
Sonic 1 has no battery save, and this page keeps nothing in browser storage on purpose — your ROM is asked for again after a reload.
