Doom Builder is an advanced map editor specifically built for the CodeImp games based on the Doom community, including Strife, Doom, Heretic, Doom II, Hexen, and other source ports that have become popular with gamers. It is an open source development based game licensed under GNU GPL. Its popularity stems from the original 1993 game Doom and its being open source, so every developer and map maker can easily inject their own tweaks in it.
Doom Builder has a dedicated Forums section where other users and map makers converge to report bugs, suggest alternate fixes, and help with the editing. Its popular features include lots of customizability, prefabricated maps, use of advanced drawing code, and viewing in 3D mode. It also offers an advanced script editor for FraggleScript and ACS. In 3D mode, users can start by editing walls and floors. The advanced script editor enables users to edit any text-based lump with autocomplete, syntax highlighting, and tooltips for function definition.
Doom Builder is now deprecated by its second version which contains more features, plugins and continued support. The new version includes the following plugins: Comments panel, copy and paste sector properties, nodes viewer, stair sector builder, statistics plugin, tag range, and Visplane explorer. Every plugin is also open source.