Megawad

A megawad is a fan-made PWAD that, according to the idgames archive definition, contains 15 or more levels, or nears the size of a commercial or registered IWAD.

Megawads may be the effort of one person, such as Gwyn Williams's Vile Flesh megawad, or of many people, such as the Doomworld community megawad project Community Chest 2. Whether a solo or group effort, excellent megawads require a huge time investment and can require months or years to create. A megawad may well represent a Doom mapper's collective lifetime works, such as Jan Van der Veken's Classic Episode, which is mostly a collection of levels previously released as stand-alone wads.

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. Megawads can sometimes exceed the size of the registered and commercial IWADs, but surely they are well over the size of the shareware IWAD.

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
 * Chex Quest 3, though its mainly marketed as a 3rd party IWAD.

Episode replacement

 * Phobos: Anomaly Reborn
 * Knee-Deep in ZDoom

Full game replacement

 * 10 Sectors
 * Alien Vendetta
 * Claustrophobia 1024
 * Community Chest
 * Community Chest 2
 * Community Chest 3
 * Congestion 1024
 * Cyberdreams
 * Eternal Doom
 * GothicDM
 * Hell Revealed
 * Hell Revealed 2
 * Icarus: Alien Vanguard
 * Memento Mori
 * Memento Mori II
 * NeoDoom
 * Newdoom Community Project
 * Newdoom Community Project II
 * Plutonia 2
 * Prayers Of Armageddon
 * Requiem
 * Scythe
 * Scythe 2
 * Speed of Doom
 * Whispers of Satan
 * ZPack - Random Maps for ZDoom

Episode replacement

 * Dark 7
 * The Darkening
 * The Darkening Episode 2