JED is one of the two availabe level editors for the games Jedi Knight and Mysteries of the Sith, the other editor being JKEdit. JED was designed by Alexei Novikov for use in the creation of new levels and the modification of existing levels for JK/MotS levels. It is a freeware program available from many on-line locations, such as the JK Editors Hub.
JED's chief purpose is the creation of level geometry, but it can also be used for the creation of 3DOs, JK/MotS 3D objects. JK/MotS level architecture is made up of sectors which are created and shaped by JED's cleave tool, extruding, scaling, and occasionally vertex editing. As opposed to the brush system of more recent game engines, JK and MotS use sectors. Put simply, brushes are walked on, sectors are walked inside of. In order for the walkplayer to move around in JK/MotS, it must be inside of a sector. Multiple sectors are joined by the adjoin feature of JED. This allows the player to walk between sectors.
JED has been reissued in many different versions, the latest of which is JED Beta version 0.951 that came out in 2002. In 2005, Alexei Novikov came out of retirement to work on a newer version of JED, one that will hopefully take full advantage of the Sith 2 engine's new features when it is finally released.