KIO (KDE Input/Output) is a system library incorporated into KDE Frameworks and KDE Software Compilation 4. It provides access to files, web sites and other resources through a single consistent API. Applications, such as Konqueror and Dolphin, which are written using this framework, can operate on files stored on remote servers in exactly the same way as they operate on those stored locally, effectively making KDE network-transparent. This allows for an application like Konqueror to be both a file manager as well as a web browser.

KIO Slaves (renamed to KIO Workers during the development of KDE Frameworks 6 ) are libraries that provide support for individual protocols (e.g. WebDAV, FTP, SMB, SSH, FISH, SFTP, SVN, TAR).

The KDE manual app KHelpCenter has a KIOSlaves (KIOWorkers in Frameworks 6) section that lists the available protocols with a short description of each.