Doom WADs are package files for the computer game Doom or its sequel Doom II, 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 levels, graphics and other game data — and played a vital part in spawning the mod-making culture which is now commonplace for first-person shooters. Thousands of WADs have been created for Doom, ranging from single custom levels to full original games; most of these can be downloaded for free 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.