IDDT

The automap is normally a partial view of a Doom level, revealing the layout as you explore it. IDDT turns that limited perspective into something much closer to a complete blueprint, making hidden geometry and the positions of things on the map considerably easier to understand. It is particularly handy when you want to study how a level is constructed rather than simply find your way through it.

How the Code Works

IDDT operates in three successive stages, cycling with each activation while the player is in automap mode:

• First use: the automap expands to reveal all unexplored areas of the current level, including invisible linedefs that the standard Computer Area Map power-up does not display.
• Second use: the display advances further to overlay the positions of all things — every monster, item, decoration, and player start — as markers on the map.
• Third use: the automap reverts to its normal state, showing only the areas the player has physically explored.

One immediately notable behavior distinguishes IDDT from nearly every other Doom cheat: it produces no acknowledgment message at the top of the screen. Most codes announce themselves (iddqd prints “Degreelessness Mode On”; idkfa prints “Very Happy Ammo Added”), but IDDT operates silently. This makes it easy to activate without interrupting the feel of play.

Nightmare! Skill Level Exception

Doom’s fifth and hardest skill level, Nightmare!, disables virtually all cheat codes as part of its extreme difficulty design. The Doom Wiki’s skill level article confirms that every cheat code other than idclev and iddt is turned off on Nightmare!, though certain source ports or re-releases handle this restriction differently or introduce workarounds of their own. IDDT’s survival of the Nightmare! lockout reflects its nature as a navigation and orientation aid rather than a combat advantage — it reveals the map, not invincibility or ammo.

In the Doom Classic Unity port and the Doom + Doom II re-release the Nightmare! cheat restriction itself works differently, so this distinction doesn’t apply there.

Multiplayer Usage

In cooperative multiplayer sessions, IDDT requires a slightly different input method. According to the Doom cheat codes reference, the player must first press T and then type the code while holding ALT. This workaround exists because the standard chat input in multiplayer intercepts keystrokes, requiring the modified entry method to route the code correctly to the cheat handler.

The “DT” in IDDT

The “id” prefix shared by most Doom cheat codes is a nod to id Software itself. The “DT” suffix is explicitly documented as standing for Dave Taylor, who was part of the core Doom programming team. Taylor’s initials appear only in this one cheat, making IDDT a small personal signature embedded in the game’s code — a tradition id Software programmers embraced across their cheat roster (compare the DQD of IDDQD, the KFA of IDKFA, and similar personal or inside-joke references).

Relationship to the Computer Area Map

It is worth noting the distinction between IDDT and the Computer Area Map power-up (also obtainable via the idbehold A cheat). The power-up reveals all linedefs and sectors but does not expose invisible linedefs or thing positions. IDDT’s first stage goes further by including those invisible linedefs, and its second stage adds thing markers entirely absent from the power-up’s display. The two are complementary: a player running both will see the fullest possible automap picture the engine can produce.

Source Port Behavior

Behavior across source ports is broadly consistent with the original, but individual ports may adjust the visual presentation of thing markers, add color coding to different thing types, or extend IDDT’s revealed data with port-specific information. The core three-stage toggle mechanic, however, is standard across Doom-engine descendants that maintain cheat-code compatibility. Ports targeting demo compatibility — such as those in the PrBoom and DSDA-Doom lineage — preserve the original behavior closely to maintain accurate playback of recorded demos that rely on consistent engine state.

The automap’s role in Doom is not merely navigational; veteran players use it to track monster positions, plan routes through unexplored territory, and identify secrets. IDDT elevates the automap from a floor-plan viewer to a comprehensive tactical display, making it one of the more practically useful cheats in the game’s arsenal — even if its absence of a confirmation message means newcomers sometimes wonder whether it activated at all.