: If you want to play for free legally, you can download the original 9-level shareware episode from the Doom Wiki Shared Files or play it directly in your web browser via emulation sites like DOS.Zone .
: You can buy the verified, complete version of the game digitally on established PC storefronts like Steam or GOG . Ultimate Doom Free Download
If you tell me what operating system you are using, I can guide you on how to get the classic shareware version running safely. : If you want to play for free
While the first episode of the original 1993 game was famously released as free shareware, the complete expanded edition known as The Ultimate Doom is a commercial product that must be purchased. Ultimate Doom Free Download