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Documentation Index

Fetch the complete documentation index at: https://mintlify.com/rommapp/romm/llms.txt

Use this file to discover all available pages before exploring further.

RomM ships with a built-in EmulatorJS integration that lets you play retro ROMs directly in your web browser — no plugins, no installs. Flash games (.swf) are also supported through the RuffleRS renderer, which runs seamlessly alongside EmulatorJS.

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Supported Systems

EmulatorJS covers most major retro platforms, including NES, SNES, Game Boy, Game Boy Color, Game Boy Advance, Nintendo 64, Nintendo DS, Sega Genesis/Mega Drive, Sega Saturn, PlayStation 1, Atari 2600/5200/7800, PC Engine/TurboGrafx-16, arcade via MAME, and many more. RuffleRS handles Adobe Flash (.swf) titles.
Not all ROM formats are supported by every core. If a game does not load, check that your ROM’s file extension matches what the underlying core expects. Refer to the EmulatorJS documentation for per-core format details.

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Enabling and Disabling

Both EmulatorJS and RuffleRS are enabled by default. You can turn either off with environment variables in your Docker deployment: 
# Disable in-browser play via EmulatorJS
DISABLE_EMULATOR_JS=true

# Disable in-browser Flash playback via RuffleRS
DISABLE_RUFFLE_RS=true

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Playing a Game

1

Open the game detail page

Navigate to any ROM in your library and open its detail page.
2

Click Play

Press the Play button to launch the EmulatorJS player. The ROM is streamed directly from your RomM server into the browser-based emulator.
3

Configure controls (optional)

Use the in-player controls menu to remap buttons, or pre-configure them in config.yml (see below).
RomM’s player integrates save-state and screenshot controls directly into the game detail page. After playing, return to the detail page to upload, download, or manage your save files and states.

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Configuration in config.yml

All EmulatorJS options live under the emulatorjs key in your config.yml file.

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Debug Mode

Set debug: true to have EmulatorJS log all available core option names to the browser console. This is useful when you want to know what keys to use in the settings section. 
emulatorjs:
  debug: true

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Per-Core Settings

Use emulatorjs.settings to pass core-specific options. The key is the exact core name as reported by EmulatorJS. A special default key applies its values to every core. 
emulatorjs:
  settings:
    parallel_n64:       # Exact core name
      vsync: disabled
    snes9x:
      snes9x_region: ntsc
    default:            # Applied to all cores
      fps: show

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Controls Mapping

Use emulatorjs.controls to define button mappings per core and per player. Each player index (0 = Player 1, 1 = Player 2, …) contains a map of button indices to their keyboard (value) and controller (value2) assignments. Every button in the core’s layout must have an entry. Refer to the EmulatorJS control mapping docs for the full list of button indices per core. 
emulatorjs:
  controls:
    snes9x:
      0:        # Player 1
        0:      # Button index — a mapping for EACH button must be set!
          value: x          # Keyboard mapping
          value2: BUTTON_2  # Connected controller mapping
      1:        # Player 2
      2:        # Player 3
      3:        # Player 4

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Cache Limit

cache_limit sets the maximum size (in bytes) that EmulatorJS will cache per ROM in the browser. Set to null (the default) to use the browser’s default behaviour. 
emulatorjs:
  cache_limit: 536870912  # 512 MB, for example

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Batch Bootup and Auto-Unload

emulatorjs:
  disable_batch_bootup: false  # Set true to disable simultaneous asset loading
  disable_auto_unload: false   # Set true to keep the emulator in memory when hidden
OptionDefaultDescription
disable_batch_bootupfalseWhen true, EmulatorJS loads assets one-at-a-time instead of in parallel.
disable_auto_unloadfalseWhen true, the emulator core stays alive even when its container is not visible.

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Save Files

EmulatorJS maintains in-browser save data (SRAM) automatically while a game is running. RomM can sync these saves back to server storage so your progress is preserved across sessions and devices.
To back up or transfer saves, navigate to the game detail page after playing. RomM will detect any new or changed saves and offer to sync them to the server. See the Saves & States guide for the full sync workflow.

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RuffleRS (Flash Games)

RuffleRS is RomM’s built-in Flash player. When a ROM file has a .swf extension, RomM automatically routes it through RuffleRS instead of EmulatorJS. No extra configuration is needed — RuffleRS is active by default unless you set DISABLE_RUFFLE_RS=true in your environment.
RuffleRS supports a large subset of ActionScript 2 and ActionScript 3 games, but compatibility with all Flash content is not guaranteed. Check the Ruffle compatibility database if a specific game does not run correctly.

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