Megawad

A megawad is a fan-made PWAD that, according to the idgames archive definition, contains 15 or more levels.

Megawads may be the effort of one person - such as Thomas van der Velden's Revolution!, Erik Alm's Scythe series or Gwyn Williams's Vile Flesh - or of many people, such as the Memento Mori series, the Alien Vendetta megawad or the Doomworld Community Chest series. Whether a solo or group effort, excellent megawads require a huge time investment and can require months or years to create. A megawad may as well represent a Doom mapper's collective lifetime works, such as Adam Windsor's Demonfear compilation or Jan Van der Veken's Classic Episode, which are mostly collections of levels previously released as stand-alone PWADs.

Because a megawad is such a massive undertaking, quality megawads are few and far between. However, they are almost always the most anticipated PWAD releases, as well as the best remembered.

Episode replacement
An episode replacement (or simply episode) is a set of fan-made levels containing a similar amount of levels as an episode of the game the episode replacement was made for. Most episode replacements therefore include eight or nine levels, which is comparable to original Doom's episode structure of eight levels and a secret level.

Full game replacement

 * 2002: A Doom Odyssey
 * ConC.E.R.Ned
 * Doom the Way id Did
 * Base Ganymede: Complete
 * Wonderful Doom

Episode replacement

 * Double Impact
 * Classic Episode
 * Crusades
 * Fava Beans
 * Knee-Deep in ZDoom
 * Phobos: Anomaly Reborn
 * The Singularity Complex I
 * Thy Flesh Turned Into a Draft-Excluder

Full game replacement

 * 10 Sectors
 * Alien Vendetta
 * Back to Saturn X
 * Claustrophobia 1024
 * Claustrophobia 1024 2
 * Community Chest
 * Community Chest 2
 * Community Chest 3
 * Community Chest 4
 * Congestion 1024
 * Demonfear
 * Eternal Doom
 * Going Down
 * GothicDM
 * Hell Revealed
 * Hell Revealed 2
 * Icarus: Alien Vanguard
 * Jenesis
 * Kama Sutra
 * Memento Mori
 * Memento Mori II
 * NeoDoom
 * Plutonia 2
 * Plutonia: Revisited Community Project
 * Requiem
 * Resurgence
 * Reverie
 * Revolution!
 * Scythe
 * Scythe 2
 * Speed of Doom
 * Unholy Realms
 * Valiant
 * Vile Flesh
 * Whispers of Satan
 * ZPack - Random Maps for ZDoom

Episode replacement

 * Combat Shock 2
 * Dark7
 * The Darkening
 * The Darkening Episode 2
 * Dystopia 3
 * Lunatic
 * Scythe X
 * SlayeR (WAD)
 * Stardate 20X6
 * Suspended in Dusk
 * UAC Ultra
 * Vanguard