Editing Doom modding (section)

===Source port era===
{{Main|Doom source ports}}
Around 1997, interest in ''Doom'' WADs began to decline, as attention was drawn to newer games with more advanced technology and more customizable design, including id Software's own ''[[Quake (video game)|Quake]]'' and ''[[Quake II]]'', but a dedicated following continued into the new century, with modern ''Doom'' modding becoming more popular than ''Quake'' and ''Quake II'' modding.

On December 23, 1997, id Software released the source code to the [[Doom engine|''Doom'' engine]], initially under a restrictive license. On October 3, 1999, it was released again under the terms of the [[GNU General Public License|GNU GPL-2.0-or-later]]. With the source code available, it became possible for programmers to modify any aspect of the game, remove technical limitations and [[Software bug|bug]]s, and add entirely new features.

These engine modifications, or [[List of Doom source ports|''Doom'' source ports]], have since become the target for much of the WAD editing activity, and with the decline of [[MS-DOS]], using a source port became the only feasible way to play ''Doom'' for most people. Several source ports are in active development, and ''Doom'' retains a strong following of WAD creators.