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The safest way to keep Game Boy or Game Boy Color progress is to treat the cartridge save as a file-transfer job: read the cartridge with a compatible reader/writer, save an untouched backup on your computer, then copy a correctly named save file into the handheld emulator’s save directory. To move progress back, export the emulator’s ordinary in-game save and use the reader/writer to restore it to the cartridge. Emulator save states are a different format and should not be substituted for the game’s normal save file.
What actually transfers: an in-game save versus a save state
A Game Boy game’s in-game save is the progress written by the game itself when you choose its save command. That is the data you normally transfer between a physical cartridge and an emulator.
A save state is an emulator snapshot. It records an exact point in execution, often including memory and emulator-specific information that does not exist as a normal cartridge save. A state can be useful for resuming play on the same emulator, but it is not automatically interchangeable with a cartridge save.
| File type | Purpose | Typical location in OnionOS | Safe transfer assumption |
|---|---|---|---|
| In-game save | Progress created by the game’s own save system | Saves/CurrentProfile/saves/[CORENAME] |
Can usually be moved when the file format, filename, core and game all match |
| Save state | Emulator snapshot for returning to an exact moment | Saves/CurrentProfile/states/[CORENAME] |
Do not rename or copy it as a cartridge save without device-specific documentation |
OnionOS documents these as separate folders and formats in its FAQ. The official Analogue Pocket page also describes capturing and loading save states during cartridge play; that feature does not establish a general file-export method for moving a save state to another emulator.
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What you need before touching the cartridge
- A compatible Game Boy cartridge reader/writer. The GBxCart RW supports Game Boy, Game Boy Color and Game Boy Advance cartridges and is designed to back up and restore saves through a computer.
- A computer and a data-capable USB cable. The product documentation lists Windows, Mac and Linux support and recommends Windows for the easiest out-of-box experience.
- The handheld’s storage card or USB file access. You need to place the save in the directory used by the handheld’s operating system and emulator core.
- Free storage for multiple backups. Keep the original cartridge dump unchanged, then make a working copy for renaming or conversion.
- The exact ROM filename and core. The save’s base filename generally has to match the ROM, and OnionOS requires case-sensitive matching.
A reader/writer is required for the physical cartridge side of the operation. Copying files on an SD card can move a save that already exists on the handheld, but it cannot read a save directly from an original cartridge or write one back to that cartridge.
Compare the two transfer methods
| Method | Reads an original cartridge? | Writes an original cartridge? | Backup and restore features | Best use |
|---|---|---|---|---|
| Manual SD-card or USB copying | No; it handles files already present on the computer or handheld | No | Depends on your own file-copy routine | Moving an ordinary save between a computer and an emulator handheld |
| Game Boy cartridge reader/writer | Yes, when the cartridge is supported | Yes, when the cartridge and save type are supported | The GBxCart RW software and manuals document PC backups, restore operations and dated backup options | Cartridge-to-computer backup and computer-to-cartridge restoration |
Before buying any reader, verify the current hardware revision, software support and the specific game’s save type in the seller’s documentation. The GBxCart RW manuals are product-specific; the Rev. 39 manual is available at this PDF, while a later Rev. 43 manual is available at this PDF.
Move a save from an original cartridge to a handheld emulator
1. Read the cartridge and create an untouched backup
- Close the game and remove the cartridge from the original console.
- Connect the compatible reader/writer to the computer and insert the cartridge according to its instructions.
- Use the reader’s save-backup function, not a ROM-only operation. The GBxCart RW manual describes a cartridge backup saved on the computer as
<Gametitle>.sav. - Give the original dump a clear name such as
GameTitle-cartridge-original.sav, but do not alter its contents. Make a second working copy before changing an extension, converting a format or testing a restore.
The manual describes confirmation before overwriting a cartridge and date/time-stamped backup options. Those safeguards are useful, but they do not replace an independent copy stored somewhere else.
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On OnionOS, [CORENAME] means the folder belonging to the RetroArch core that runs the game. Do not guess the folder from the game’s title. Check where another working save for the same system is stored, or use the core name shown by the handheld’s software.
For current OnionOS layouts, the documented in-game save directory is:
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Saves/CurrentProfile/saves/[CORENAME]OnionOS also documents an older stock-Miyoo or earlier-layout location:
RetroArch/.retroarch/saves/[CORENAME]Use the path that matches the OnionOS version and storage layout actually installed on your device. Do not place the file in the states directory.
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3. Match the save format and filename
OnionOS says that most in-game saves should use the .srm extension. It documents that a .sav file can be renamed to .srm in common cases; other formats may require a conversion tool. This advice is specific to OnionOS and its documented “most cases,” not a universal rule for every emulator handheld.
- Copy the working duplicate of the cartridge backup.
- Rename only the duplicate if the handheld requires
.srm. - Make the filename before the extension identical to the ROM filename, including capitalization. For example, if the ROM is
PokemonBlue.gb, the save should use the same base name rather than an unrelated title or a second copy suffix. - Place the file inside the correct core folder under
Saves/CurrentProfile/saves.
Do not delete the original .sav backup after renaming. A filename change does not convert incompatible save data; it only changes what the operating system calls the file.
4. Deal with an existing save state
If you launched the game on OnionOS before importing the cartridge save, the emulator may have an existing state for that title. OnionOS instructs users to remove the corresponding state from:
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Saves/CurrentProfile/states/[CORENAME]First copy that state to a separate backup location. Then remove the state associated with the game and launch the title normally so the emulator reads the imported in-game save. Removing a state can discard the exact resume point represented by it; preserving a copy lets you restore it later if needed.
5. Start the game and verify progress
- Eject or safely disconnect the storage card, if your handheld requires that before booting.
- Launch the game without loading a save state.
- Use the game’s own load or continue menu and check a few unmistakable details: the save slot, party or inventory, level, map location, or other progress that you know was present on the cartridge.
- Do not overwrite the cartridge or delete your computer backup until the handheld shows the expected data.
The GBxCart RW Rev. 39 manual recommends verifying Game Boy saves with an emulator such as BGB. That is a verification option described by the manual, not a guarantee that every game or save format will behave identically in every emulator.
Move emulator progress back to the original cartridge
The reverse direction uses the same two boundaries: first obtain the handheld’s ordinary in-game save, then use a cartridge reader/writer to write it. A save state is not a substitute.
1. Save normally in the game
Inside the emulator, use the game’s own save command and wait for the write to finish. Exit cleanly if the handheld’s operating system provides an option to close the game, then locate the resulting file in the core’s save directory. On OnionOS, that is normally Saves/CurrentProfile/saves/[CORENAME].
Copy the file to the computer and retain the exact original as a backup. If you renamed a cartridge .sav file to .srm for OnionOS, keep the original extension and a separate copy rather than treating the renamed file as a new, independently verified format.
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2. Confirm compatibility before writing
- Confirm that the save belongs to the same game release and region when the game has multiple releases.
- Confirm that the reader/writer supports the cartridge and its save type.
- Check that the file is an ordinary in-game save, not a state, cheat file or emulator-specific snapshot.
- Keep the existing cartridge save in a separate backup before connecting the cartridge for restoration.
Save-file compatibility is not guaranteed merely because two devices run the same title. Different cores, revisions or save formats can require conversion, and the reader’s documentation is the authority for the supported cartridge and file type.
3. Use the reader’s restore function
- Connect the reader/writer and insert the cartridge.
- Open the software’s save-restore operation and select the computer copy of the emulator’s in-game save. The GBxCart RW manual calls this operation Restore Save.
- Read the overwrite warning carefully. The software confirms before replacing the cartridge save, but proceed only after checking the filename and backup.
- Allow the write to finish without disconnecting the reader or cartridge.
- Return the cartridge to compatible original hardware and load the game through its normal menu to verify the imported progress.
Do not rely on the overwrite prompt as your only recovery plan. If the write fails or the file is incompatible, the independent cartridge backup is what lets you restore the previous progress.
Why a save state from one device may not work on another
Save states depend on the emulator implementation, core version, memory layout and sometimes the exact ROM image. Even when two handhelds use RetroArch, their state files may be stored in different locations or generated by different cores. Renaming a state to .sav or .srm does not turn it into the game’s normal save.
If your only copy of progress is a state, look for a device-specific way to load that state and then use the game’s own save command to create a normal in-game save. Whether that works depends on the original emulator and game. Do not delete the state until the newly created in-game save has been tested.
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The Analogue Pocket officially supports Game Boy, Game Boy Color and Game Boy Advance cartridges and advertises save-state capture and loading. Its current support page lists firmware version 2.7 dated September 4, 2026, and a manual dated April 18, 2024; check the current Pocket support documentation before applying firmware-specific instructions. The official pages do not provide a general file-based export/import procedure between the Pocket and another emulator, so there is no universal Pocket save-file workflow to apply by assumption.
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Real-time-clock games can behave differently after a transfer
Some Game Boy games use a cartridge real-time clock for events tied to the time of day or day of the week. A correctly transferred save can therefore load successfully while the game’s clock-based behavior differs from what you saw on original hardware.
OnionOS documents a specific limitation for the Miyoo Mini: it has no built-in clock. By default, OnionOS adds four hours at each boot; that offset is configurable. Time advances while the game is running and stops when the device is shut down. This behavior is specific to the Miyoo Mini running OnionOS and should not be generalized to every emulator handheld.
For an RTC-dependent title, record the clock-related setting or event timing before switching devices, and expect to adjust the handheld’s configuration or in-game clock behavior. A save transfer preserves file data; it cannot give a device a continuously running clock that it does not have.
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- Check that the file is in the save folder for the core actually running the game, not merely a similarly named system folder.
- Compare the save’s base filename with the ROM character by character, including uppercase and lowercase letters.
- Confirm that the extension is one the OnionOS setup expects. In the common documented case, that means
.srm; a.savfile may need to be renamed, while other formats may need conversion. - Check whether the game was launched before the file was copied. If so, preserve and remove the matching state from the states folder as OnionOS documents.
- Make sure the file is not zero bytes, duplicated with an automatic “copy” suffix, or still inside a compressed archive.
The imported file loads, but progress is wrong
- Stop playing and keep the suspect file unchanged.
- Compare it with the untouched cartridge dump or the last known-good emulator backup.
- Check that you selected the correct game release and did not mix saves from similarly named ROMs.
- Try the reader’s or emulator’s documented compatibility/conversion method rather than repeatedly overwriting the cartridge.
The cartridge will not accept the restored save
- Verify that the reader/writer supports that cartridge family and save type.
- Confirm that you selected the ordinary in-game save, not a state file.
- Restore the original cartridge backup if necessary, then test the game on original hardware before attempting another conversion.
- Check the reader’s current manual and software version; instructions and supported revisions can change.
The game clock is wrong
Separate a clock problem from a save-file problem. If the save slot and other progress are present but time-based events are shifted, the device’s RTC behavior is the likely cause. On the Miyoo Mini with OnionOS, account for the documented four-hour boot adjustment and the fact that time stops while the device is off.
A backup routine that prevents permanent loss
- Keep one untouched cartridge dump in a folder named for the game and cartridge.
- Create a dated working copy before renaming, converting or importing it.
- After a successful emulator import, copy the working save again before playing further.
- Before restoring to a cartridge, export the current cartridge save and label it with the date and device.
- Keep at least one backup away from the handheld’s SD card so a failed card or accidental overwrite does not remove every copy.
- Test each restored save through the game’s normal load menu, not only by checking that a file exists.
This routine leaves you with recovery points for the cartridge, the emulator and every conversion step. It also makes it clear which file is original and which one has been modified.
Practical checklist
- Is this an ordinary in-game save rather than a save state?
- Did you create an untouched cartridge backup before editing anything?
- Does the handheld use the correct core folder and save path?
- Does the save base name match the ROM exactly, including case?
- Does the extension match the handheld’s documented format?
- Did you preserve or remove a conflicting state according to the device’s instructions?
- Have you verified the expected progress in the game before overwriting or deleting another copy?
- Could an RTC limitation explain different time-based behavior?
Bottom line
For a physical Game Boy or Game Boy Color cartridge, the reliable bridge is cartridge → reader/writer → computer backup → handheld save folder. To return progress, reverse that path with the reader’s save-restore function. Keep independent backups, match the handheld’s core, path, filename and format, and treat save states as a separate feature. That approach preserves the game’s real save data without assuming that an emulator snapshot can travel between unrelated devices.
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