How to play retro cartridges on iPhone and iPad from backups you own

To play retro cartridges on iPhone or iPad, you need each cartridge as a file and an app that runs it. A USB cartridge reader copies a cartridge you own into a game file and, if the game saves, a separate save file. Move them to the phone with AirDrop, iCloud Drive or a cable, import the game into Bitfold, our free retro console app, and add the save from the game’s Details.

Bitfold turns the whole screen into a pocket console, as our launch post shows. It comes with twelve original games, includes and downloads no commercial ones and never goes online, so every other game on its shelf is a file you bring. You can try three of the Originals in your browser first, five minutes a day with no sign-up, but importing your own games needs the app.

This guide follows a cartridge from the reader to the shelf in Bitfold 1.1, on the App Store since 6 November 2026, and says what the app’s code does at each step. It ends with a troubleshooting table and a checklist.

What you need to play retro cartridges on iPhone

• A cartridge you own. Bitfold’s shelf says the app includes and downloads no commercial games, and asks you to play only cartridge images you own. Laws on copying games differ by country, so check the rules where you live. This guide isn’t legal advice.
• A USB cartridge reader, and a computer to run its software.
• An iPhone or iPad on iOS 17 or later.

Bitfold’s help screen also suggests homebrew and freely licensed games from independent developers, which import the same way as a backup.

Make a cartridge backup with a USB cartridge reader

A cartridge reader, also called a cartridge dumper, is a small device with a cartridge slot and a USB cable. Its software, on your computer, copies the cartridge into files. The game comes from the cartridge’s read-only memory and your progress, if the game saves, from its battery-backed memory. So a full backup is two files, and they reach Bitfold by different routes.

Bitfold reads the header inside the game file to tell monochrome games from colour ones, so any accepted extension will do. It refuses game files over 8 MB, the most the header’s size code can describe. The cartridge types it knows keep 512 bytes to 128 KB of save memory, and its save import takes files of up to 256 KB.

Keep both files on your computer as well. Bitfold’s privacy policy says removing the app removes your saves, and that iCloud and Finder backups of the device include them.¹

Get the files onto your iPhone or iPad

Bitfold registers with iOS as an app that opens .gb, .gbc, .sgb and .cgb files and zips, so iOS can offer it when you open one. There are five ways in.

Apple says AirDrop accepts and saves items on its own between devices on the same Apple Account, and that some items land in the Files app.² Import those with +. The Finder’s Files tab lists apps that support file sharing, which Bitfold does, and Apple points Windows users to its Apple Devices app.³

Bitfold scans only the top level of its folder, for game files and zips. It moves each file into a subfolder called Imported before reading it, so a file that fails isn’t retried at every launch, and a repeated name gets a number, as in Game 2.gb. Since 1.1, a game you tap in the folder opens straight away, and a file there that can’t be imported gets an alert. The shelf keeps its own copy of each game, so you can empty Imported whenever you like.

Import ROM files on iPhone and what the shelf does with them

Tap + at the top right of the shelf and pick one or more files. The picker accepts .gb, .gbc, .sgb, .cgb and .zip. For each file, Bitfold does four things.

1. It checks that the file is a game, as described further down.
2. It identifies the game by the CRC-32 checksum and size of the image, so a second copy gets “… is already on your shelf”.
3. It copies the game into its own storage, so you can delete the file you picked.
4. It names the game after the file, dropping anything in brackets and turning underscores into spaces. My_Game (backup 2).gb becomes My Game. If nothing is left, it uses the title in the header.

An alert confirms the import (“Added My Game.”), and the game joins Your Cartridges, sorted A to Z. Touch and hold a cartridge for Play, Details, Add to Favorites and Delete. Details has Rename in its ⋯ menu and shows the header title, the hardware the game was made for and your play time.

Monochrome games get grey cartridges, games with extra colour get charcoal ones, and colour-only games get see-through purple. Monochrome games play in the green Pea Soup palette until you pick another in Settings.

Until you play, the label shows a controller icon and the title’s initials. After about 25 seconds of play in one go, Bitfold keeps the frame on screen as the label art, once, with no button to retake it. The code counts 1,500 frames, so fast-forward gets there sooner, and the power-on animation, the pause menu and rewinding don’t count.

Zips, including ones made on a Mac

Bitfold opens a .zip and takes the first game file inside, ignoring the rest. A zip of several games adds one, and a .sav packed beside a game stays behind. Unzip such a zip first. Apple says tapping a ZIP file in the Files app creates a folder with its contents.⁴ Then pick all the games at once.

Bitfold 1.1 fixed “zips with hidden files in them, like ones made on a Mac”, as its release notes put it. A hidden file’s name starts with a dot, as in ._Game.gbc, and can end in a game’s extension. 1.0 took the first file with a game’s extension, so a hidden one listed first could be read instead, and the import failed. 1.1 skips names that start with a dot, as it already skipped folders and anything under __MACOSX.

Entries must be stored or compressed with deflate. Bitfold refuses password-protected zips, other compression methods, zips over 64 MB and games inside over 8 MB.

Saves: import a battery save and keep your progress

Bitfold takes your cartridge’s save separately, one game at a time. The + picker takes only games and zips, a zip gives up only its first game, and Bitfold’s folder ignores .sav files. To bring a save in:

1. Import the game.
2. Touch and hold its cartridge on the shelf and tap Details.
3. Under Saves, tap Import Battery Save and pick the .sav file.
4. Start the game and continue from its own menu, as you would on the cartridge.

Bitfold accepts any file that isn’t empty and is 256 KB or smaller, whatever its extension, and doesn’t check that it belongs to the game. It replaces the game’s battery save without asking, so export the old one first if it matters. It also deletes the game’s automatic save, so the next start can’t resume over the save you brought. An empty or bigger file gets “That file isn’t a battery save.”

If the file runs past the game’s save memory, the emulation core reads the extra bytes as the cartridge clock when it knows their layout. Otherwise it resets the clock and flags the reset to the game. A cartridge clock then runs in step with the phone’s clock, even while Bitfold is closed.

Once a game has a battery save, an Export button beside Import Battery Save hands battery.sav to the share sheet, for AirDrop or Files. From your computer, the reader’s software can write it back to the cartridge, if it supports that.

From then on, Bitfold writes battery.sav within about 2 seconds of the game saving. It writes it again, with an automatic save state, when you leave the game or switch apps. The next start resumes on the same frame, unless Resume Where You Left Off is off in Settings or the battery save is newer, as after a crash.

The four save-state slots, under Save and Load in the console’s Menu, can’t be imported or exported. The battery save is the only progress that moves between the app and a cartridge. Our post on save states, rewind and fast-forward explains each kind of save.

A file that differs by a single byte is a different game with its own saves. If a fresh read of a cartridge gives a different file, export the old copy’s battery save and import it into the new one.

Delete a game from the shelf

Since 1.1, Delete is in the long-press menu. Touch and hold an imported cartridge, tap Delete and confirm with Delete Cartridge and Saves. Delete in the ⋯ menu in Details does the same. The dialog says it “removes the cartridge image, its battery save and all save states from Bitfold”. The label art and any cheat codes go too, because Bitfold removes the game’s whole folder.

There’s no undo, so export the battery save first. Importing the file again brings the game back with no saves and a new label. The twelve Originals have no Delete. A file in Bitfold › Imported stays until you remove it in Files.

When a file isn’t a game

Bitfold checks every image before it reaches the shelf. It must be at least 336 bytes, enough for the whole header, and no more than 8 MB. The header can’t be all zero or all FF bytes. If its checksum is wrong, its two size codes must be ones real cartridges use, since homebrew sometimes leaves the checksum unset but has real size codes.

That last check is new in 1.1, and it keeps files that aren’t games off the shelf. For random bytes, the checksum matches by chance 1 time in 256, and both size codes land on real values 54 times in 65,536. So about 1 random file in 210 still gets through. Bitfold doesn’t compare a file’s length with its header, so a read that stopped early can still import.

Every failure shows the same line with the file’s name, such as “Game.gbc isn’t a cartridge image Bitfold can read.” The alert is titled Nothing Imported after + or a drag onto the shelf, and Couldn’t Import for files from Bitfold’s folder or other apps. Several failures read “3 files couldn’t be read.”

Troubleshooting a Bitfold import

Each row comes from a case in Bitfold 1.1’s import and save code.

Where these details come from

The limits, messages and behaviour come from Bitfold 1.1’s source code and its App Store release notes, and the iOS steps from Apple’s support pages. We haven’t tested any particular cartridge reader for this post.

A checklist for each cartridge

• Clean the contacts, read the cartridge and keep both files on your computer.
• Send the game over by AirDrop, by iCloud Drive and +, or through On My iPhone › Bitfold.
• Check that the alert says Added.
• Import the .sav from Details before you play, then continue from the game’s menu.
• Spend your first half minute on a screen you’d like as the label.
• Export the battery save before you delete a game or import a new read of it.

Bitfold also comes with twelve games of its own: see the guide to all twelve Bitfold Originals and what Bitfold 1.1 added.

Frequently asked questions