To perform the conversion, you will need specific utilities. There isn't one single "magic button" tool, but rather a suite of powerful editors that handle the job perfectly.

Caveat: This works for simple mods. But if you want proper folder structure, read on.

Converting to PK3 is not just about file extensions; it is about future-proofing your mod. You gain access to GZDoom's hardware rendering, UDMF map format support, and the ability to mix and match assets without naming collisions.

The most recommended tool for any Doom editing task is SLADE 3. It is not just a converter but a full-featured archive editor. What is the difference between a WAD a a .pk3? : r/DoomMods