Note that 'official' in this context refers to provision of the content by id Software. This, however, requires the merging of the PWAD in question with its target IWAD, converting said PWAD into a standalone IWAD. Thanks to DMAPINFO and, mainly, the ability of its engine of running, regardless of the base game, in The Ultimate Doom mode should the loaded PWAD contain an E1M1 lump and, conversely, in Doom II mode should it contain a MAP01 lump, most of the curated PWADs are made available to both games.

This effectively makes Final Doom free for all owners of either Classic Doom titles on.

The two Final Doom IWADs are available as official add-ons for both The Ultimate Doom and Doom II. Last but not least, the written legal consent of all involved authors for each and every included asset is mandatory, so that they all have to be contactable by id Software in order to license their work. Official add-ons are curated to ensure they are playable within the raised limits of Doom Classic, and to avoid potential copyright infringement in their content. Since console manufacturers do not usually allow players to use third-party content unless vetted by the publisher of the game, the official add-ons system allows a selection of modifications to be downloaded and played instead of being limited to the IWADs. The official add-ons are third-party PWADs that can be downloaded for free from to be played with the Doom Classic Unity port.

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