Doom Builder is a Doom level editor with full support for ZDoom editing, including the "Game-in-Hexen" and "Game-in-UDMF" map formats. It is being developed by Pascal vd Heiden (alias CodeImp) and is free software, licensed under the terms of the GNU General Public License. Popular features include lots of customizability, prefabs, advanced drawing code, and a 3D mode that lets you browse and edit your levels in real time.
See also the Doom Builder ACS configuration.
The current version of Doom Builder is Doom Builder 2, a total rewrite. The last version of Doom Builder 1 is 1.68.
The original Doom Builder was written mostly in Visual Basic. It can run on Windows 98, 2000, or XP, but not on newer versions of Windows (Vista, 7 and above). It can be used to create maps in the Doom and Hexen formats; but it is generally outdated and unsupported. It is able to parse DECORATE lumps to find custom actors, and also supports graphics defined in TEXTURES.
Doom Builder 2
A complete rewrite in C#, DB2 (or Doom Builder 2) was the first map editor to support UDMF in addition to the older binary map formats. Doom Builder 2 requires, at minimum, Microsoft Windows XP, but it is crucial to have Microsoft .NET Framework 3.5 installed within the system - regardless of the Microsoft Windows version.
Doom Builder X
A fork of DB2 intended to update and maintain the DB2 workflow and interface without drastic changes.
GZDoom Editing Plugin
An alternate version of the 3D visual mode, which was never completed. It shows 3D floors and slopes. It has been replaced by GZDoom Builder, which does not use it.
Doom Builder 64
A fork of DB2 specialized on creating maps for Doom64 EX. It cannot be used to edit maps in the formats supported by ZDoom.
Another fork of DB2 specialized on creating maps for ZDoom and GZDoom. It boasts enhanced support for ZDoom features such as showing slopes, 3D floors, and dynamic lights in visual mode, displaying models, and parsing MAPINFO, GLDEFS and MODELDEF lumps in addition to DECORATE to obtain the data it needs to give an accurate preview of the level in 3D mode.
A fork of GZDoom Builder mainly meant to keep the editor up-to-date with the latest GZDoom once the author of GZDB left the community.
Both versions of Doom Builder include a DECORATE parser used to obtain relevant information (such as editor number, Radius, Height, Scale, and so on) from custom actors. Additional information can be conveyed with keys in the form of special comments inserted within an actor's declaration block. GZDB and GZDB-BF also include parsers for MAPINFO and ZScript, and editor keys can be read if they are in an actor's Default block.
See Editor keys for a centralized full list.