From a RetroPie post:
WAD is a file format which stands for "Where's All the Data?" If Doom was a console, then modern source ports like zDoom would be the emulator and WADs would be the ROMs. There are two kinds of WADs: IWADs and PWADs. IWADs are full games while PWADs are patches which are applied to games. Most Doom mods are distributed as PWADs to be used on top of the base game.
List of WADs[]
| Name | Type | Where to get | Notes |
|---|---|---|---|
| Heretic: Shadow of the Serpent Riders | Commercial title | GOG store page | |
| HeXen: Beyond Heretic | Commercial title | GOG store page | |
| HeXen: Deathkings of the Dark Citadel | Commercial title | GOG store page | Includes the WAD from HeXen: Beyond Heretic, and it needs to be in the same folder as the WAD from HeXen:DotDC for the latter to start. |
| The Ultimate DOOM | Commercial title | GOG store page | |
| DOOM II + Final DOOM | Commercial title | GOG store page (bundle) | |
| Chex Quest | Freeware, mod | Developer's site | |
| FreeDoom | Free and Open Source Software | Project's page | |
| HacX | Freeware | Project's page | |
| StarDoom | Freeware, mod | Project's page | |
| HDoom (+18) | Freeware, mod | Developer's page (+18) | Requires a source port that can run PK3 files, e.g. GZDoom. |
| Hedon Bloodrite | Commercial title | GOG store page |