The official editor for Fallout 3 and Fallout: New Vegas, called the G.E.C.K. (named after the in-game Garden of Eden Creation Kit), is currently available for free download. This tool allows PC users to create and add their own content to the game.
The release of the G.E.C.K. provides the community with tools that will allow players to expand the game. Users can create, modify, and edit any data for use with Fallout 3, from building landscapes, towns, and locations to writing dialogue, creating characters, weapons, creatures, and more.
The G.E.C.K. has an interface similar to The Elder Scrolls Construction Kit.