Custom IOS

Custom IOS, aka cIOS, are third-party IOS files that are installed on the wii. Most cIOS's are used for pirating. They are often made by using a base IOS with desirable features, such as USB support or Rockband microphone support and modified to install to a different slot such as 254 and then add extra features, such as restoring the trucha bug and adding piracy related functions.

Due to its heavy links with piracy, the word cIOS is generally avoided by most of the anti-piracy community, instead preferring more generic terms such as "patched IOS" when writing programs that require them.