[1] The series usually focuses on the exploits of an unnamed space marine (often referred to as Doomguy or Doom Slayer) operating under the auspices of the Union Aerospace Corporation (UAC), who fights hordes of demons and the undead to save Earth from an apocalyptic invasion.

[4] Outside of combat mechanics, Doom levels often feature mazes, colored key cards and hidden areas.

The technical changes allowed for greater flexibility with the level design, such as the ability to adjust the geometry of the map during play.

Id did not allow the title to be called Doom 3, as the name was being reserved for a potential return to the franchise after the development of Quake.

[14] By 2000 a new non-Doom game was being designed, but id staff had a "lack of enthusiasm" for the project, and strongly desired to remake the original Doom instead.

John Carmack, among others, announced internally that they were working on a Doom game- and would continue to do so unless the company fired them.

[18] Using the new id Tech 4 engine, numerous technical improvements were made over the classic series, allowing greater realism and interactivity.

It includes all of the content from Doom 3: BFG Edition (the main campaign, Resurrection of Evil and The Lost Mission), except for multiplayer.

Bethesda marketing vice president Pete Hines stated in retrospect that "it wasn't Doom enough".

John Carmack, one of the few remaining veterans from the development of the classic series still present at id, left the studio that November.

[30] A VR spinoff entitled Doom VFR was released in 2017 to generally positive reception, with reviewers discussing the movement controls in particular- which were well made albeit hidden behind menus.

[32] 2018 marked the 25th anniversary of the franchise, and saw the Doom Slayer included as a playable character in id Software's Quake Champions.

The episode was released for free via Romero's website in 2019, with a paid version available that included a soundtrack by guitarist Buckethead.

Some commentators cited the timing of the release, which coincided with a wave of interest in gaming worldwide amid restrictions on social gathering during the COVID-19 pandemic.

[45] A spin-off for mobile platforms Android and iOS, Mighty Doom, was developed by Alpha Dog Games and released in March 2023.

[46] Microsoft announced that it was shutting down Alpha Dog in May 2024; this resulted in the discontinuation of Mighty Doom in August.

A set of four novels based on Doom were written by Dafydd ab Hugh and Brad Linaweaver, and were published between June 1995 and January 1996 by Pocket Books.

The books, listed in order, are titled Knee Deep in the Dead, Hell on Earth, Infernal Sky and Endgame.

[61] In 2020, Critical Role published a fifth edition Dungeons & Dragons module entitled Doom Eternal: Assault on Amaros Station.

The game was written by Christopher Lockey and Matthew Mercer, and received a digital release via the Critical Role store on December 16, 2020.

[62][63][64] In 2005, Universal Pictures released the first live-action film adaptation, titled Doom, which starred Karl Urban and Dwayne Johnson.

In 2019, Universal released a second live-action film adaptation direct-to-video, titled Doom: Annihilation starring Amy Manson.

In 1996, Next Generation ranked the series as the 19th top game of all time, for how "despite the hundreds of copycat titles, no one has ever been able to equal id's original, pulsing classic.

In 2009, GameDaily included "the Marine" on its list of "ten game heroes who fail at the simple stuff" for his inability to look up and down in the original series.

[124] UGO Networks ranked him fourth on its 2012 list of best silent protagonists in video games, noting his courage to continue in silence even when he faces Hell's army.