Doom WAD is the default format of package files for the video game Doom and its sequel Doom II: Hell on Earth, that contain sprites, levels, and game data. WAD stands for Where's All the Data? Immediately after its release in 1993, Doom attracted a sizeable following of players who created their own mods for WAD files—packages containing new levels or graphics—and played a vital part in spawning the mod-making culture which is now commonplace for first-person shooter games. Thousands of WADs have been created for Doom, ranging from single custom levels to full original games; most of these can be freely downloaded over the Internet. Several WADs have also been released commercially, and for some people the WAD-making hobby became a gateway to a professional career as a level designer.