Free online GCZ to WBFS converter

What the GCZ format is

GCZ is Dolphin’s compressed optical-disc image format for Nintendo GameCube and Wii games. Dolphin can create GCZ files when compressing dumped ISO images, and its emulator can open them directly. GCZ compression is lossless, so the original disc data can be recovered without changing the game content.

What the WBFS format is

WBFS is a Wii Backup File System image format designed for storing Wii disc backups on hard drives, SD cards, and USB devices used with compatible Wii loaders. It can reduce storage use by omitting unused disc sectors, but it is not a general-purpose filesystem and cannot be mounted like ISO or ZIP data. Compatibility depends on the loader and on whether the source image is a Wii disc.

How to convert GCZ to WBFS

Using Wiimms ISO Tools

Wiimms ISO Tools is the most direct desktop option because it can read Dolphin GCZ images and write Wii-compatible WBFS output.

1. Install Wiimms ISO Tools for your operating system.
2. Place the source file, such as game.gcz, in a directory with enough free space for the converted image.
3. Run:

wit copy game.gcz game.wbfs

If the program does not infer the desired output from the extension, specify the output format explicitly according to the installed version’s command help, or convert the GCZ to ISO first and then create the WBFS file:

wit copy game.gcz game.iso
wit copy game.iso game.wbfs

Check the resulting image with:

wit verify game.wbfs

Use a destination on a filesystem that supports large files. FAT32 limits individual files to 4 GiB, so Wii software may split the output into parts such as game.wbfs and game.wbf1; the loader must support split WBFS files.

Using Dolphin and a Wii backup manager

1. Open Dolphin and use Tools → Convert File to decompress game.gcz to an ISO image, if the installed Dolphin version provides that operation.
2. Open the ISO in a Wii backup utility that supports WBFS creation, such as Wii Backup Manager.
3. Choose the option equivalent to Transfer → WBFS file or Add → Drive → Transfer, select the destination, and let the utility create the WBFS image.

The exact menu names vary by Wii backup utility. Do not rename .gcz to .wbfs; changing the extension does not change the image format.

Using the online converter

You can also convert the file for free on 101convert.com without installing software. Uploading a disc image requires trusting the service with the game data and having enough bandwidth for a large file.

Compatibility and limitations

First identify the disc type. A GCZ containing a Wii disc is an appropriate source for a Wii WBFS image. A GameCube GCZ may convert technically, but many Wii loaders and Wii backup managers do not accept GameCube content in WBFS form; use the format required by the intended GameCube loader instead.

The conversion is normally lossless at the game-data level, although WBFS may discard unused padding sectors to reduce size. It does not remove regional restrictions, encryption requirements, or loader compatibility problems. Keep the original GCZ until the WBFS file has passed verification and successfully loads in the target hardware or emulator.