Save Sync Coverage¶
Why some saves sync and others don't. The mechanics live in Save File Sync Architecture; this page explains the coverage envelope — which save files the per-game model can and cannot reach — and the strategy for the gaps. The user-facing result is the Save sync support matrix.
The per-game discovery model¶
Save discovery is exact-name probing, not a directory scan. For an installed ROM whose file stem is rom_name, the
sync looks for exactly <saves_dir>/<rom_name><ext> for each extension in a fixed list, and uploads the ones that
exist. There is no glob, no listdir, no pattern match.
This is a deliberate bijection: one ROM → one set of <rom_name>.<ext> files in the save folder. It maps perfectly
onto libretro's own SRAM convention, where the save file mirrors the ROM name. Everything that doesn't fit that shape is
invisible to the sync.
Two hard properties follow, and they define the entire coverage envelope:
- The filename must be the ROM stem. A file named anything else — a fixed card name (
pcsx-card2.mcd,vmu_save_A1.bin), or a name with a slot/unit infix (game.1.mcr) — is never probed. - The file must live in the save folder. A save in RetroArch's system directory (Flycast VMUs), in a per-emulator
subdirectory (
mame/nvram/), or next to the ROM (savefiles_in_content_dir) is never seen.
The explicit removed-game cleanup starts with this exact-path projection and adds path-safe filenames already persisted
for that ROM in RomSaveSyncState.files. This is an identity-backed exception to the filename rule, not directory
discovery: cleanup never scans for new names. Class (c), unknown fixed/shared names, unresolved uninstalled layouts, and
save states are left physically untouched and recorded as warnings where applicable. If two installed local rows project
the same canonical current-save path, that path is shared ownership; purging one owner may copy it into recovery but
cannot remove it while another owner remains.
The extension list is a small static map keyed by the RetroDECK system (the normalized value from resolve_system /
platform_map, not the raw RomM platform slug — keying by system keeps the lookup aligned with the save directory,
cores, and gamelists, which are all system-keyed): a default of .srm / .rtc / .sav, plus per-system overrides
(nds → .dsv, segacd → .brm, saturn → .bkr/.bcr/.smpc, ngp/ngpc → .flash/.ngf, pokemini →
.eep, and amiga/amigacd32 → .nvr).
How RomM stores saves¶
RomM treats a save as a file blob keyed by (rom_id, slot), with an emulator tag (which becomes a storage
subdirectory) and an MD5 content_hash. It stores the bytes the client sends and leaves their meaning to the client —
there is no save_type or memory-card concept, and each save belongs to a single ROM. This format-agnostic design keeps
the server simple and works for any client; RomM's own in-browser player (EmulatorJS) uses the same path, uploading one
save blob per (game, core).
Because both the server and our discovery are organised per game, two things follow. Supporting a new per-game
save format is a client-side change — the server already accepts the file as-is. And a shared card has no per-game
identity to map onto a (rom_id, slot) record, so any shared-card handling is a client-side modelling decision (see
below), not something the server provides or prevents.
The three coverage classes¶
Every core's save behavior falls into one of these (plus "no save"):
| Class | Shape | What it needs |
|---|---|---|
| (a) | Per-game, single-token <rom>.<ext>, save folder |
Just add <ext> to the override map. No architecture change. |
| (b) | Per-game, but a slot/unit infix (<rom>.1.mcr, <rom>.A1.bin) |
Infix-aware discovery and download-target derivation (the current code drops the infix), plus multi-file-per-ROM support. |
| (c) | Shared card (one file, many games), fixed name, or outside the save folder | Breaks the per-game model. Not solvable by an extension — see strategy below. |
Class (a) is pure upside. Class (b) is bounded engineering that stays inside the per-game model. Class (c) is the genuinely hard one.
Strategy for class (c)¶
The emulation ecosystem has already converged on the answer, and it aligns with this project's "no assumptions, the user decides on ambiguity" stance:
- No tool merges binary card images. Block-level merge of a shared
.mcr/.ps2/.rawis a confirmed dead end. The only options are isolate (per-game) or pick-one (whole-file). - Prefer per-game mode. Modern emulators default to it (DuckStation per-game cards; Beetle PSX / PCSX ReARMed slot 0; PCSX2 Folder Memory Cards; Dolphin GCI folders). Where the launch core supports per-game cards, that path collapses class (c) into class (a)/(b) and maps cleanly onto per-game sync.
- For an unavoidable shared card, treat it as one device-global blob: whole-file, last-writer-wins, with conflict detection that warns instead of clobbering (the Ludusavi model), and rely on the existing version history as the recovery net. Never present it as per-game; never merge.
- Sync SRAM, not save states. Save states are core- and version-coupled and not portable across devices; in-game saves are.
- The per-game card format is emulator-specific. A per-game card written by the RetroArch PCSX2 core is not
byte-compatible with standalone PCSX2. The sync key/format must match the core the user actually launches with — which
is exactly what RomM's
emulatorsubdirectory captures.
Roadmap mapping¶
- (a) — extension-map additions, candidate for incremental delivery; research/verification tracked in #237.
- (b) — infix-aware per-game discovery (PS1 multi-card, Flycast per-game VMU, 3DO NVRAM); research in #237, implementation under the save-format epic #255.
- (c) — shared/system-dir handling under #255 (save formats), #151 (Dreamcast VMU), and #129 (standalone emulators) — all v2.0.
Evidence level, and where the audit has since disagreed¶
The classification below was a desk audit: libretro documentation plus core source reading, one pass, no per-core observation. emu-atlas is auditing the same ground with an explicit evidence grade per core (source / binary / live), and as of its 2026-07-24 snapshot has reached 17 of RetroDECK's 159 libretro cores and none of the 22 standalone emulators. Treat an unrevised row here as a documented expectation, not a verified fact.
Every core the atlas audit has reached and disagreed with, corrected here:
| Core | Was | Audit finding |
|---|---|---|
opera |
✅ .srm |
Wrong. RETRO_MEMORY_SAVE_RAM returns NULL — there is no RetroArch-side .srm at all. NVRAM goes to <save_dir>/opera/per_game/<rom_stem>.<version>.srm, the version coming from opera_nvram_version. Per-game, but subdir + infix → class (b). |
flycast |
🔴 (c) shared | Shared is the shipped default (reicast_per_content_vmus=disabled → <system_dir>/dc/vmu_save_A1.bin …). The core is per-game capable: the VMU A1 / All VMUs modes root at savefile_directory; their filename scheme is unestablished. |
pcsx2 |
🔴 (c) shared | Shared is the shipped default (pcsx2_shared_memory_cards=enabled → <system_dir>/pcsx2/memcards/Mcd00{1,2}.ps2). Disabled, slot 1 is <save_dir>/<rom_stem>.ps2 — class (a), reachable by an extension-map entry alone. |
neocd |
🔴 (c) shared | Per-game capable: path.cpp:137-168 proves a per-content mode alongside the frontend save RAM path. Load precedence between the two is unobserved. |
ppsspp |
🔴 (c) shared | Not established. The shipped sort override is known; the save subtree and its granularity are not. |
dolphin |
🔴 (c) .gci |
Not established. RetroDECK's prepared dolphin-emu subtree suggests a different root, but no core-written save has been observed. |
azahar |
absent | RetroDECK now ships Azahar for n3ds where this table still listed Citra. Verdict suspect — prepared save subtree suggests a deviation, nothing observed. |
Two of these are strategically relevant. pcsx2 and flycast are not class (c) by nature — they are class (c) as
configured, which is exactly the "prefer per-game mode" path below, and it makes PS2 the cheapest of the shared-card
systems to support. The opera correction runs the other way: 3DO was published as syncing and does not.
The row set below is also a 2026-06-04 snapshot of RetroDECK's core list and has drifted (Azahar is one instance).
Full core reference¶
Per-core classification from the audit of every RetroArch core RetroDECK can launch. ✅ syncs today · 🟡 (a)
per-game, extension not listed yet · 🟠 (b) per-game with a slot/unit infix · 🔴 (c) shared / out-of-folder · ⚪
no battery save · ❓ unverified. Non-.srm rows are libretro-documented and await on-device confirmation. Snapshot:
2026-06-04, with the rows above revised 2026-08-02.
All 156 cores, classified
| Core | Status | Save file(s) | Naming / dir | Used by (slugs) |
|---|---|---|---|---|
boom3_libretro |
🔴 (c) | .save |
system_dir / content | doom |
boom3_xp_libretro |
🔴 (c) | .save |
system_dir / content | doom |
cannonball_libretro |
🔴 (c) | .xml |
shared_fixed_name / system | ports |
cap32_libretro |
🔴 (c) | .sna |
single_token_nonstandard / content | amstradcpc, gx4000 |
dosbox_svn_libretro |
🔴 (c) | — | system_dir / saves | dos, pc |
easyrpg_libretro |
🔴 (c) | .lsd, .lyn, .dyn, .lgs |
single_token_nonstandard / content | easyrpg |
flycast_libretro |
🔴 (c) | .bin |
shared_fixed_name / system | arcade, atomiswave, consolearcade, dreamcast, mame +3 |
mame2000_libretro |
🔴 (c) | .nv |
shared_fixed_name / system | arcade, cps, cps1, cps2, cps3 +1 |
mame2003_libretro |
🔴 (c) | .nv |
shared_fixed_name / saves | arcade, cps, cps1, cps2, cps3 +1 |
mame2003_plus_libretro |
🔴 (c) | — | single_token_nonstandard / saves | arcade, cps, cps1, cps2, cps3 +1 |
mame2010_libretro |
🔴 (c) | .nv |
system_dir / saves | arcade, cps, cps1, cps2, cps3 +1 |
mame_libretro |
🔴 (c) | .nv |
system_dir / saves | apple2, apple2gs, arcade, arcadia, astrocde +29 |
mess2015_libretro |
🔴 (c) | — | system_dir / system | mess |
neocd_libretro |
🔴 (c) | .srm |
shared_fixed_name / saves | neogeocd, neogeocdjp |
openlara_libretro |
🔴 (c) | .dat |
shared_fixed_name / saves | ports |
pcsx2_libretro |
🔴 (c) | .ps2 |
shared_fixed_name / system | ps2 |
prboom_libretro |
🔴 (c) | .dsg |
shared_fixed_name / saves | doom |
px68k_libretro |
🔴 (c) | — | system_dir / system | x68000 |
scummvm_libretro |
🔴 (c) | — | system_dir / system | scummvm |
vitaquake2-rogue_libretro |
🔴 (c) | — | shared_fixed_name / content | quake |
vitaquake2-xatrix_libretro |
🔴 (c) | — | shared_fixed_name / content | quake |
vitaquake2-zaero_libretro |
🔴 (c) | — | shared_fixed_name / content | quake |
vitaquake2_libretro |
🔴 (c) | — | shared_fixed_name / content | quake |
mednafen_psx_hw_libretro |
🟠 (b) | .srm, .mcr |
infix / saves | psx |
mednafen_psx_libretro |
🟠 (b) | .srm, .mcr |
infix / saves | psx |
opera_libretro |
🟠 (b) | .srm |
version infix / saves subdir opera/per_game |
3do |
pcsx_rearmed_libretro |
🟠 (b) | .srm, .mcd |
infix / saves | psx |
swanstation_libretro |
🟠 (b) | .mcd, .mcr |
infix / saves | psx |
tyrquake_libretro |
🟠 (b) | .sav |
infix / saves | quake |
virtualjaguar_libretro |
🟠 (b) | .srm, .cdrom.srm |
infix / saves | atarijaguar |
dosbox_pure_libretro |
🟡 (a) | .pure.zip, .save.zip |
single_token_nonstandard / saves | dos, pc, windows3x, windows9x |
kronos_libretro |
🟡 (a) | .ram |
single_token_nonstandard / saves | arcade, consolearcade, mame, saturn, saturnjp +1 |
nxengine_libretro |
🟡 (a) | .dat |
single_token_nonstandard / saves | ports |
retro8_libretro |
🟡 (a) | .p8d.txt |
single_token_nonstandard / saves | pico8 |
ardens_libretro |
❓ | — | unknown / unknown | arduboy |
azahar_libretro |
❓ | — | unknown / unknown | n3ds |
citra2018_libretro |
❓ | — | unknown / unknown | n3ds |
citra_libretro |
❓ | — | unknown / unknown | n3ds |
dolphin_libretro |
❓ | .gci, .gcs |
unknown / unknown | gc, wii |
panda3ds_libretro |
❓ | — | unknown / unknown | n3ds |
ppsspp_libretro |
❓ | — | unknown / unknown | psp |
same_cdi_libretro |
❓ | — | unknown / unknown | cdimono1 |
wasm4_libretro |
❓ | — | unknown / unknown | wasm4 |
DoubleCherryGB_libretro |
✅ | .srm, .rtc |
single_token_default / saves | gb, gbc |
blastem_libretro |
✅ | .srm |
single_token_default / saves | genesis, megadrive, megadrivejp |
bsnes-jg_libretro |
✅ | .srm, .rtc |
single_token_default / saves | satellaview, sfc, snes, snesna, sufami |
bsnes_hd_beta_libretro |
✅ | .srm, .rtc |
single_token_default / saves | satellaview, sfc, snes, snesna, sufami |
bsnes_libretro |
✅ | .srm |
single_token_default / saves | gb, gbc, satellaview, sfc, snes +2 |
bsnes_mercury_accuracy_libretro |
✅ | .srm |
single_token_default / saves | satellaview, sfc, snes, snesna, sufami |
desmume2015_libretro |
✅ | .dsv |
single_token_default / saves | nds |
desmume_libretro |
✅ | .dsv |
single_token_default / saves | nds |
fbneo_libretro |
✅ | .nv, .fs |
single_token_default / saves | arcade, cps, cps1, cps2, cps3 +5 |
fceumm_libretro |
✅ | .srm |
single_token_default / saves | famicom, fds, nes |
gambatte_libretro |
✅ | .srm, .rtc |
single_token_default / saves | gb, gbc |
gearboy_libretro |
✅ | .srm, .rtc |
single_token_default / saves | gb, gbc |
gearcoleco_libretro |
✅ | .srm |
single_token_default / saves | colecovision |
geargrafx_libretro |
✅ | .srm |
single_token_default / saves | supergrafx |
gearsystem_libretro |
✅ | .srm |
single_token_default / saves | gamegear, mark3, mastersystem, multivision, sg-1000 |
genesis-plus-gx-expanded-rom-size-paprium_libretro |
✅ | .srm |
single_token_default / saves | megadrive, megadrivejp |
genesis_plus_gx_libretro |
✅ | .srm, .brm |
single_token_default / saves | gamegear, genesis, mark3, mastersystem, megacd +5 |
genesis_plus_gx_wide_libretro |
✅ | .srm, .brm |
single_token_default / saves | gamegear, genesis, mark3, mastersystem, megacd +5 |
geolith_libretro |
✅ | .srm, .nv, .mcr |
single_token_default / saves | arcade, mame, neogeo |
gpsp_libretro |
✅ | .srm |
single_token_default / saves | gba |
mednafen_ngp_libretro |
✅ | .flash |
single_token_default / saves | ngp, ngpc |
mednafen_pce_fast_libretro |
✅ | .srm |
single_token_default / saves | pcengine, pcenginecd, tg16, tg-cd |
mednafen_pce_libretro |
✅ | .srm |
single_token_default / saves | pcengine, pcenginecd, supergrafx, tg16, tg-cd |
mednafen_pcfx_libretro |
✅ | .srm |
single_token_default / saves | pcfx |
mednafen_saturn_libretro |
✅ | .bkr, .bcr, .smpc |
single_token_default / saves | saturn, saturnjp |
mednafen_supafaust_libretro |
✅ | .srm |
single_token_default / saves | sfc, snes, snesna |
mednafen_supergrafx_libretro |
✅ | .srm |
single_token_default / saves | supergrafx, tg16 |
mednafen_vb_libretro |
✅ | .srm |
single_token_default / saves | virtualboy |
mednafen_wswan_libretro |
✅ | .srm |
single_token_default / saves | wonderswan, wonderswancolor |
melonds_libretro |
✅ | .sav |
single_token_default / content | nds |
melondsds_libretro |
✅ | .srm |
single_token_default / saves | nds |
mesen-s_libretro |
✅ | .srm |
single_token_default / saves | gb, gbc, satellaview, sfc, sgb +2 |
mesen_libretro |
✅ | .srm |
single_token_default / saves | famicom, fds, nes |
mgba_libretro |
✅ | .srm |
single_token_default / saves | gb, gba, gbc, sgb |
mupen64plus_next_libretro |
✅ | .srm |
single_token_default / saves | n64, n64dd |
nestopia_libretro |
✅ | .srm |
single_token_default / saves | famicom, fds, nes |
noods_libretro |
✅ | .srm |
single_token_default / saves | gba |
parallel_n64_libretro |
✅ | .srm |
single_token_default / saves | n64, n64dd |
picodrive_libretro |
✅ | .srm |
single_token_default / saves | gamegear, genesis, mark3, mastersystem, megacd +7 |
pokemini_libretro |
✅ | .eep |
single_token_default / saves | pokemini |
potator_libretro |
✅ | .srm |
single_token_default / saves | supervision |
puae2021_libretro |
✅ | .nvr |
single_token_default / saves | amiga, amiga1200, amiga600, amigacd32, cdtv |
puae_libretro |
✅ | .nvr |
single_token_default / saves | amiga, amiga1200, amiga600, amigacd32, cdtv |
quasi88_libretro |
✅ | .srm |
single_token_default / saves | pc88 |
quicknes_libretro |
✅ | .srm |
single_token_default / saves | famicom, nes |
race_libretro |
✅ | .ngf |
single_token_default / saves | ngp, ngpc |
sameboy_libretro |
✅ | .srm, .rtc |
single_token_default / saves | gb, gbc, sgb |
sameduck_libretro |
✅ | .srm, .rtc |
single_token_default / saves | megaduck |
smsplus_libretro |
✅ | .srm |
single_token_default / saves | gamegear, mark3, mastersystem |
snes9x2005_plus_libretro |
✅ | .srm |
single_token_default / saves | satellaview, sfc, snes, snesna, sufami |
snes9x2010_libretro |
✅ | .srm |
single_token_default / saves | satellaview, sfc, snes, snesna, sufami |
snes9x_libretro |
✅ | .srm |
single_token_default / saves | satellaview, sfc, snes, snesna, sufami |
stella2014_libretro |
✅ | .srm |
single_token_default / saves | atari2600 |
stella2023_libretro |
✅ | .srm |
single_token_default / saves | atari2600 |
stella_libretro |
✅ | .srm |
single_token_default / saves | atari2600 |
tgbdual_libretro |
✅ | .srm, .rtc |
single_token_default / saves | gb, gbc |
tic80_libretro |
✅ | .srm |
single_token_default / saves | tic80 |
vba_next_libretro |
✅ | .srm |
single_token_default / saves | gba |
vbam_libretro |
✅ | .srm |
single_token_default / saves | gb, gba, gbc |
vice_x128_libretro |
✅ | .nvr, .d64, .d71, .d81 |
single_token_default / saves | c64 |
vice_x64_libretro |
✅ | .nvr, .d64, .d71, .d81 |
single_token_default / saves | c64 |
vice_x64sc_libretro |
✅ | .nvr, .d64, .d71, .d81 |
single_token_default / saves | c64 |
vice_xplus4_libretro |
✅ | .nvr, .d64, .d71, .d81 |
single_token_default / saves | plus4 |
vice_xscpu64_libretro |
✅ | .nvr, .d64, .d71, .d81 |
single_token_default / saves | c64 |
vice_xvic_libretro |
✅ | .nvr, .d64, .d71, .d81 |
single_token_default / saves | vic20 |
yabasanshiro_libretro |
✅ | .bkr, .bcr, .smpc |
single_token_default / saves | saturn, saturnjp |
yabause_libretro |
✅ | .srm |
single_token_default / saves | saturn, saturnjp |
81_libretro |
⚪ | — | none / none | zx81 |
a5200_libretro |
⚪ | — | none / none | atari5200 |
arduous_libretro |
⚪ | — | none / none | arduboy |
atari800_libretro |
⚪ | — | none / none | atari5200, atari800, atarixe |
b2_libretro |
⚪ | — | none / none | bbcmicro |
bluemsx_libretro |
⚪ | — | none / none | colecovision, msx, msx1, msx2, msxturbor +2 |
cdi2015_libretro |
⚪ | — | none / none | cdimono1 |
chailove_libretro |
⚪ | — | none / none | chailove |
crocods_libretro |
⚪ | — | none / none | amstradcpc, gx4000 |
dice_libretro |
⚪ | — | none / none | arcade, mame |
dirksimple_libretro |
⚪ | — | none / none | daphne, laserdisc |
dosbox_core_libretro |
⚪ | — | none / none | dos, pc |
ecwolf_libretro |
⚪ | — | none / none | ports |
fbalpha2012_cps1_libretro |
⚪ | — | none / none | cps, cps1, fba |
fbalpha2012_cps2_libretro |
⚪ | — | none / none | cps, cps2, fba |
fbalpha2012_cps3_libretro |
⚪ | — | none / none | cps, cps3, fba |
fbalpha2012_libretro |
⚪ | — | none / none | arcade, cps, cps1, cps2, cps3 +2 |
fbalpha2012_neogeo_libretro |
⚪ | — | none / none | fba |
fmsx_libretro |
⚪ | — | none / none | msx, msx1, msx2 |
freechaf_libretro |
⚪ | — | none / none | channelf |
freeintv_libretro |
⚪ | — | none / none | intellivision |
frodo_libretro |
⚪ | — | none / none | c64 |
fuse_libretro |
⚪ | — | none / none | zxspectrum |
gw_libretro |
⚪ | — | none / none | gameandwatch, lcdgames |
handy_libretro |
⚪ | — | none / none | atarilynx |
hatari_libretro |
⚪ | — | none / none | atarist |
holani_libretro |
⚪ | — | none / none | atarilynx |
lowresnx_libretro |
⚪ | — | none / none | lowresnx |
lutro_libretro |
⚪ | — | none / none | lutro |
mednafen_lynx_libretro |
⚪ | — | none / none | atarilynx |
mojozork_libretro |
⚪ | — | none / none | zmachine |
mrboom_libretro |
⚪ | — | none / none | ports |
mu_libretro |
⚪ | — | none / none | palm |
nekop2_libretro |
⚪ | — | none / none | pc98 |
np2kai_libretro |
⚪ | — | none / none | pc98 |
o2em_libretro |
⚪ | — | none / none | odyssey2, videopac |
prosystem_libretro |
⚪ | — | none / none | atari7800 |
squirreljme_libretro |
⚪ | — | none / none | j2me |
superbroswar_libretro |
⚪ | — | none / none | ports |
theodore_libretro |
⚪ | — | none / none | moto, to8 |
uzem_libretro |
⚪ | — | none / none | uzebox |
vecx_libretro |
⚪ | — | none / none | vectrex |
vircon32_libretro |
⚪ | — | none / none | vircon32 |
virtualxt_libretro |
⚪ | — | none / none | dos, pc |
vitaquake3_libretro |
⚪ | — | none / none | quake |
x1_libretro |
⚪ | — | none / none | x1 |