While the Steam version is cheaper, the GOG.com version has no DRM and offers bonus free content.
The 1.112fm patch fixes various bugs and adds multiplayer. Digital distribution versions already include this patch as do some retail re-releases.
Kentie's Deus Exe is an updated executable that integrates support for various features. It does not work with the GameStop (Impulse) version of Deus Ex.
This fix will replace the existing deusex.exe file within the folder. If you want to be able to uninstall it, backup the main executable beforehand.
Kentie's Direct3D 10 renderer improves compatibility with modern systems and adds native support for various features including anti-aliasing, anisotropic filtering and multi-monitor resolutions.
A number of mods have been released for Deus Ex which include improvements to texture quality and gameplay adjustments:
Deus Ex: New Vision replaces the vast majority of the game's texture files with HD remakes, drastically improving the visual appeal of the game. It is compatible with Kentie's Custom Launcher, however note that to use these improved textures an additional renderer is required. 2 are included in the New Vision download, one for DirectX and one for OpenGL, and a video demonstrating full installation of the mod with Kentie's Launcher can be found here.
Deus Ex HDTP (High Definition Texture Project) is a mod aimed to remodel and retexture the majority of the game's assets. The mod is currently in beta stages. The newest version can be downloaded either through Mod DB or from the Off Topic Productions forum thread, which also list all the progress on the updates.
GMDX (Give Me Deus Ex), winner of Moddb's 2014 Mod of the Year "Worldly Award" is a mod for the Deus Ex campaign. GMDX improves Deus Ex's AI considerably, polishes and expands upon weapon behavior, fixes bugs, expands upon and refines the RPG systems (Augmentations, skills and weapon mods) as well as a vast number of other game systems, adds a new difficulty mode, improves audio & level design, just about everything has been polished and expanded upon in GMDX except for the plot.
Shifter fixes many common annoyances with the game, including improved enemy AI and a restructured augmentation system which replaces augmentations considered obsolete by the developer of the mod. Note however that this mod makes the game significantly easier by increasing the number of skill points awarded and items dropped among other things.
The Nameless Mod is an extensive conversion of Deus Ex which provides a new storyline within the Unreal 1 engine set outside of the Deus Ex universe. This modification is fully voiced and includes many new weapons and features.
Deus Ex: Nihilum (also known as DXN, DEN and Nihilum) is a "mod taking place in an alternate Deus Ex continuity". It takes some content from other mods and provides around 10 hours of gameplay. It includes around 3.5 hours of voice work and 2 hours of new audio.
Toggled in Settings->Display or by using Alt+↵ Enter, but this doesn't affect start-up. Also, only the software renderer and Direct3D 10 renderer properly handle adjusting brightness in Windowed mode. (OpenGL renderer will adjust brightness but affects the entire screen.)
Use Deus Exe or modify DeuxEx.ini (line StartupFullscreen) to start in Windowed mode.
Generally speaking the error message will detail the subsystem in which the crash occurred in so you can narrow down the possible causes. You can also access the game's logfile (Deus Ex\system\deusex.log) for additional information.
This is usually caused by the chosen renderer. Launch Deus Ex in Safe Mode and change to a different renderer. If problems persist, try the Direct3D 10 renderer.
Depending on the resolution (e.g. 1366x768), the GUI may still be too small or too big, use AHK Injector instead.
After the release of the 1.112fm patch Ion Storm released an official SDK for the game which includes a full level editor and conversation editor. Note however that it is possible to crash the SDK by excessively spawning some items including rockets.