The Tool Desk
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Understand the two files you may be calling a “save”
A Game Boy game can write ordinary saved progress to the cartridge’s save memory. That is the file you need when moving a character, team, level, or story position between original hardware and an emulator. A cartridge reader/writer can copy that memory to a computer, where it becomes a file such as GameTitle.sav.
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An emulator can also create a save state. A state is a snapshot of the emulator, game memory, and execution point. It is useful for resuming at an exact moment, but it is not the same structure as the game’s own save data. OnionOS stores these categories in different locations: in-game saves are under Saves/CurrentProfile/saves/[CORENAME], while states are under Saves/CurrentProfile/states/[CORENAME] (OnionOS FAQ). Analogue also describes capturing and loading states during cartridge play (Analogue Pocket), but that feature does not establish a universal, file-based state-transfer format.
Copying a state, changing its extension, or renaming it to look like a .sav or .srm file will not normally produce a usable cartridge save. Always make an in-game save from the game’s own menu or save mechanic, then transfer that save file.
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What you need before starting
- The original cartridge, if you are copying progress from hardware.
- A compatible cartridge reader/writer connected to a computer. GBxCart RW documentation covers Game Boy, Game Boy Color, and Game Boy Advance cartridges, including backing up and restoring save data (GBxCart RW).
- A computer and a USB connection. The product documentation lists Windows, Mac, and Linux support and says Windows is recommended for the easiest out-of-box experience (GBxCart RW).
- The handheld’s storage card or USB file access, so you can place a save in the emulator’s expected directory.
- Enough free storage for multiple backups. Keep the original dump untouched and work from a duplicate.
- The correct emulator core and ROM. The save’s base filename and core association must match what the handheld uses.
Exact menu names and file extensions vary by reader, firmware, operating system, and emulator. The paths below are specific to OnionOS where stated; do not assume another handheld uses them.
Move a save from an original cartridge to a handheld emulator
1. Make the cartridge backup before changing anything
- Finish any in-game saving on the original Game Boy or Game Boy Color. Wait for the game to complete its save operation before powering down or removing the cartridge.
- Connect the reader/writer to the computer and insert the cartridge according to its instructions. Do not write to the cartridge during this first pass.
- Use the reader software’s save-backup function. GBxCart RW manuals describe saving a cartridge dump to the computer as a file such as
<Gametitle>.savand provide backup and restore operations (GBxCart RW Manual Rev. 39). - Give the untouched file a clear archival name, for example
GameTitle-cartridge-original-2026-10-16.sav. Keep it in a separate backup folder and make a second copy on another drive or cloud storage.
Do not overwrite this original while experimenting with extensions, conversion utilities, or emulator settings. A reader/writer can overwrite the cartridge when restoring a file; an independent backup is your recovery point.
2. Make a working copy and check the dump
Duplicate the archival file and use only the duplicate for renaming or conversion. The GBxCart manual recommends checking Game Boy saves with an emulator such as BGB; that is a verification option documented by the manual, not a guarantee that every game or modern core will behave identically (GBxCart RW Manual Rev. 39).
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Open the game with the emulator you intend to use and confirm that the expected file size and save type are recognized. If the game reports a blank save, stop and return to the untouched backup instead of saving over the file again.
3. Identify the handheld’s ROM and core names
On OnionOS, the normal destination for an in-game save is:
Saves/CurrentProfile/saves/[CORENAME][CORENAME] is the folder for the RetroArch core that runs the game. The save must be associated with the same core and ROM identity used by the handheld. A ROM placed in one system folder but launched by a different core can look for a different save location.
On an older stock Miyoo SD layout or an earlier OnionOS arrangement, the documented path is:
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RetroArch/.retroarch/saves/[CORENAME]Check the version and directory structure on the actual card before copying. Do not create a second, guessed folder if the handheld already has a current profile structure.
4. Match the extension and filename exactly
OnionOS says most in-game saves should use the .srm extension. It documents that a .sav file can be renamed to .srm in most cases, while other formats may require conversion (OnionOS FAQ). That instruction applies to OnionOS’s documented setup, not every emulator or handheld.
Rename the working copy so its base name is identical to the ROM’s name, including capitalization. For example, if the ROM is GameTitle.gbc, the usual OnionOS filename is GameTitle.srm. Do not change the game’s title, region suffix, punctuation, or case unless the core’s own documentation requires it.
| Item | Example | Why it matters |
|---|---|---|
| ROM filename | GameTitle.gbc |
The core uses this base name to locate the save. |
| OnionOS in-game save | GameTitle.srm |
Common documented extension for most saves. |
| Reader backup | GameTitle.sav |
Typical PC backup name described by the GBxCart manual. |
| State file | Stored under states/[CORENAME] |
Separate snapshot data; not a replacement for the in-game save. |
5. Copy the save to the correct folder
- Power off the handheld and remove or mount its SD card using the method recommended for that device.
- Open
Saves/CurrentProfile/saves/[CORENAME]on an OnionOS card, or the olderRetroArch/.retroarch/saves/[CORENAME]path when that layout applies. - Copy the working save file into that folder. Do not delete the cartridge archive.
- Eject the card safely, reinstall it, and boot the handheld.
If the handheld already contains a save with the same name, copy it to a separate backup folder before replacing it. This protects progress that was created on the handheld.
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If the game was launched previously, OnionOS says an existing state can cause the emulator to resume old memory instead of reading the newly imported in-game save. First copy the relevant state file somewhere safe. Then remove the corresponding state from:
Saves/CurrentProfile/states/[CORENAME]Launch the game normally and choose its in-game load option. Preserve the state backup in case you need the previous snapshot later. Never delete a state before making a copy if it contains progress that was never written through the game’s own save system.
7. Verify the imported progress
- Start the game without loading a state.
- Open the game’s save or continue menu and check the expected player, location, inventory, and play time.
- Play briefly, make a new in-game save, exit cleanly, and reopen the game to confirm that the handheld can write the file.
- Only after this check should you consider changing the cartridge or deleting any backup.
A successful file copy proves only that the file reached the directory. The game’s own load screen is the meaningful confirmation.
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Move emulator progress back to the original cartridge
1. Export the ordinary in-game save
On the handheld, save through the game’s normal menu or save mechanic. Do not rely on a quick-save state. Shut down or exit the game cleanly so the emulator flushes the save to storage.
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2. Confirm compatibility before writing
The file must represent the same game and a compatible save-memory layout as the cartridge. Region, revision, patched ROMs, and different emulator cores can affect compatibility. If the handheld used a conversion or a core-specific format, do not assume that simply changing .srm to .sav makes it valid. Use the reader, game, and core documentation to determine whether conversion is required.
If you are uncertain, keep the cartridge’s original backup and test the working file in an emulator first. A failed restore should not be your first discovery that the file is incompatible.
3. Back up the current cartridge save again
Insert the cartridge into the reader/writer and perform another read before writing. Save this second dump with a date and description, such as GameTitle-cartridge-before-restore-2026-10-16.sav. This preserves the cartridge’s current progress in case the emulator copy is wrong or you later want to revert.
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4. Use the reader’s Restore Save function
- Open the reader software and select the cartridge save-restore operation. The GBxCart RW manual labels this operation Restore Save and describes selecting the PC save file (GBxCart RW Manual Rev. 39).
- Select the working copy of the emulator’s ordinary in-game save.
- Read the confirmation carefully. The software warns that restoring will overwrite the cartridge save; confirm only after verifying the filename and backup.
- Wait for the write to finish, then perform a read-back or verification if the software offers one.
The confirmation prompt is a safety check, not a substitute for an independent backup. The manual also describes date- and time-stamped backup options; use them when available (GBxCart RW Manual Rev. 39).
5. Test on original hardware
Safely remove the cartridge from the reader and insert it into the Game Boy or Game Boy Color. Load the game through its normal continue/load menu and check the same milestones you verified on the handheld. Do not immediately create a new save until you know the restored one loaded correctly.
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Manual SD copying versus a cartridge reader/writer
These methods solve different problems. SD-card copying moves a file that already exists on an emulator. It cannot read a save that is still inside an original cartridge. A reader/writer is required for the cartridge-to-computer and computer-to-cartridge steps.
| Comparison point | Manual SD-card copying | Cartridge reader/writer |
|---|---|---|
| Reads original cartridge memory | No; it only moves files already on the card. | Yes, when the reader supports the cartridge family. |
| Writes an original cartridge | No. | Yes, with a compatible restore function. |
| Game Boy/Game Boy Color support | Depends on the handheld’s emulator and core. | GBxCart RW documentation explicitly covers Game Boy and Game Boy Color cartridges. |
| Backup and restore workflow | Copy, rename, or replace files manually. | Dedicated backup and restore operations are documented. |
| Dated backup copies | You must create and name them yourself. | The manual documents date/time-stamped backup options. |
| Computer operating systems | Depends on how the handheld storage is mounted. | The product page lists Windows, Mac, and Linux, with Windows recommended for the easiest setup. |
| Save-type handling | Must match the core’s expected extension and format. | Still must match the game and cartridge’s save type; a reader cannot make an incompatible file valid. |
Before buying any reader, verify the current hardware revision, seller listing, supported cartridge families, software version, and whether save backup and restore—not merely ROM dumping—are included.
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Some Game Boy games use a cartridge real-time clock (RTC) for time-of-day, calendar, or day-of-week events. A save-file transfer can preserve stored progress while the clock behavior changes on the destination device.
OnionOS documents a specific limitation for the Miyoo Mini: it has no built-in clock, adds four hours at each boot by default (the offset is configurable), advances game time while the device is running, and stops advancing when the device is shut down (OnionOS FAQ). This explains why an imported save can load correctly yet show unexpected in-game time. It is a Miyoo Mini/OnionOS caveat, not a rule for every handheld emulator.
If RTC events matter, record the original device’s date and time, check the handheld’s clock behavior, and avoid assuming that two systems will produce identical day/night or timed-event results. Keep the original cartridge backup in case the game’s clock-dependent state becomes undesirable.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What is and is not established for Analogue Pocket
Analogue’s official Pocket page states support for Game Boy, Game Boy Color, and Game Boy Advance cartridges and advertises save-state capture and loading during cartridge play (Analogue Pocket). Those facts do not amount to a general-purpose file-transfer procedure between Pocket and another emulator.
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For a Pocket-to-handheld or handheld-to-Pocket move, use only a documented ordinary-save export/import path for the specific firmware and storage workflow. Do not infer one from community posts, and do not copy a Pocket state as though it were a cartridge .sav. The Pocket support page lists firmware v2.7 dated 2026-09-04 and a manual dated 2024-04-18; check the current documentation before following firmware-specific instructions (Pocket Support).
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Troubleshooting by symptom
The game starts with no save
- Confirm that you copied an in-game save, not a state file.
- Check the core folder under
Saves/CurrentProfile/saves. - Match the ROM base name exactly, including capitalization and punctuation.
- On OnionOS, try the documented
.srmextension for a typical.savbackup. - Check whether the game was launched before import and remove only the corresponding state after preserving a copy.
The handheld loads an older position
An existing state may be restoring old emulator memory. Back up and remove the matching file from Saves/CurrentProfile/states/[CORENAME], then launch without loading a state. Also check for duplicate ROMs with nearly identical names; each base name can point to a different save.
The file is rejected or the save is corrupted
Restore your untouched cartridge dump or handheld backup. Check whether the ROM is a different region, revision, or patched build, and whether the emulator core expects a different save format. Do not repeatedly write a suspect file to the cartridge. A conversion may be necessary, but use a tool that explicitly supports the game’s save type rather than guessing from the extension.
The cartridge still shows old progress after restore
Read the cartridge back with the reader to confirm which data was written. If the read-back is old, repeat the restore only from a verified working copy and follow the reader’s connection, power, and confirmation procedure. If the read-back is correct but the console shows old data, power-cycle the console, reseat the cartridge, and test the cartridge on the original hardware without an emulator state involved.
Clock-based events are wrong
Separate save compatibility from RTC behavior. The save may be intact while the destination device lacks a continuously running clock or applies its own offset. Use the device-specific clock settings and documentation; do not rewrite a good save merely because a timed event differs.
A backup routine that prevents permanent loss
- Keep one untouched cartridge dump and one untouched handheld save before every transfer.
- Use working copies for renaming, conversion, and testing.
- Include the game title, source device, destination device, and date in backup filenames.
- Maintain at least one backup away from the SD card and reader computer.
- After a successful transfer, make a fresh backup from the destination before beginning another migration.
- Never overwrite the only copy when a restore dialog appears.
This process makes the direction reversible: the cartridge remains recoverable, the emulator’s prior progress remains available, and every write has a known source file.
The practical decision
If your progress currently exists only on an original cartridge, start with a reader/writer and a computer backup; SD-card copying alone cannot reach cartridge memory. If the progress is already on a handheld, copy the ordinary in-game save into the destination emulator’s documented save directory, match the core and case-sensitive ROM name, and deal with any existing state separately. When returning to original hardware, back up the cartridge again and use the reader’s restore operation only after confirming save compatibility.
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