You can find the base game on Steam and GOG . It often goes on sale for a few dollars.

The most popular way to play the Wolfenstein experience for free is through , which is available at no cost on platforms like Steam and the Microsoft Store . Originally intended as an expansion for RtCW, it was released as a standalone multiplayer-only game and remains one of the most influential team-based shooters in gaming history. Getting the Original Game (Paid & Community)

If you are looking for the original single-player campaign where you play as B.J. Blazkowicz, it is typically a paid product. However, there are various ways to acquire or enhance it today:

For a completely free and legal standalone multiplayer experience, is your best bet. If you want the full story campaign, it is recommended to buy the base game on Steam and apply the ioRTCW patch for the best performance.