PRIVATE – WS Flash Masta USB (Cartridge for WonderSwan)


Make sure you’ve talked to Ed before purchasing this, or your order may be canceled!

Use the WS Flash Masta USB to upload files from your computer to the cartridge via built-in micro USB and play them on your WonderSwan, WonderSwan Color, or SwanCrystal console.

That the “Circuit Board Only” option will need to be installed into a plastic shell before you can use it in a Wonderswan console. You can use a plastic shell from another game you already own, but you’ll need to shave/cut some of the plastic (for example to make an opening for the USB and some other parts). Check out the following links if you’d like to try to 3D print your own cartridge shell.
MyMiniFactory WS Flash Masta Shell
Thingiverse WS Flash Masta Shell

The dust cover is an original official Wonderswan cartridge enclosure.  It is not 3D-printed.

Due to variations in 3D printing, the shell that you receive may not look exactly like the photos shown here.

Please read the full description for important information.

SKU: WS-FM_v5-2-1-1 Category: Tags: , , , , ,


The WS Flash Masta USB cartridge will accept 16 ROM files (one of which will likely be a menu) via USB and allow you to play them on your WonderSwan, WonderSwan Color, or SwanCrystal game console.

To upload ROMs to the cartridge, use the software found at Most users will want to flash a ROM-selector menu to the first slot. This will allow you to select the other slots upon bootup.

Look closely at the product photo. That is what you will receive. This cartridge currently comes in a plastic shell, but it does not have a “Flash Masta” sticker. It may or may not come with a pre-attached sticker from an official game.

You can read more about this version (and previous versions) of the cartridge at our Wonderswan Flash Masta Cartridge forum.

As far as functionality goes, there are some items to be aware of. Not all ROMs work 100%. If you want to know more about what ROMs have problems, please see this forum thread about the v5.1 WS Flash Masta USB. Notice that some ROMs require a patch to work properly while a small percentage just fail to run. If any of the ROMs mentioned are of particular interest to you, I suggest that you post in that thread to see if anyone can provide more information.

Another item to make note of is that while the ROM area of the cartridge has 16 slots, the SRAM (gamesave) area does not have separate slots. This means that you can select different slots, but they will share the SRAM area. A game selection may overwrite other slot’s savegame data. Currently, playing a game may interfere with another slot’s savegame information. This may or may not be changed in the future.

If you are familiar with our previous WS Flash Masta USB cartridge (v4.4), this cartridge is intended to provide the same functionality. This 5.1 version of the cartridge is a redesign to make sourcing parts and manufacturing easier. This version also fits inside of a shell and does not require a battery to store gamesaves.

Additional information

Weight 0.1875 lbs

In 3D-Printed Shell, In 3D-Printed Shell With Random Dust Cover