‘Doom’ CAPTCHA Turns Online Security Into a Demon-Slaying Nightmare Challenge

We’ve all been there—trying to access a website, only to face the dreaded CAPTCHA. But what if, instead of matching obscured letters, ducks, or stairs, you could blast demons from hell? That’s the premise of Doom CAPTCHA, a new project that uses the classic first-person shooter Doom to prove a person isn’t a bot.

Doom CAPTCHA is the brainchild of software engineer and CEO of software developer Vercel, Guillermo Rauch, who shared a video of the project on X (formerly Twitter) on Tuesday.

“Verify you’re human by playing Doom and killing at least three enemies in nightmare mode,” Rauch said.

I built https://t.co/YtUfA7fIyM – verify you’re human by playing DOOM and killing at least 3 enemies 😁 (in nightmare mode)

powered by webassembly × libsdl, ui built in @v0 pic.twitter.com/kv6TAbJglx

— Guillermo Rauch (@rauchg) December 31, 2024

How does it work?

Using the arrow keys and space bar, players maneuver the ol’ space marine through the maze. Demons will spawn from all sides, and because you are in nightmare difficulty mode, they pack a harder punch.

However, while the controls for Doom CAPTCHA are easy enough, learning how to take on the demons—especially in nightmare mode—can be frustrating and end up taking longer than just completing a regular CAPTCHA.

“After like four tries of being an idiot, I realized if I just step forward, THEN backward, I can shoot the three dudes that spawn right in front of me, and I’m away from enemy fire,” an X user responded to Rauch’s post.

“Yeah, that’s the winning move,” Rauch replied. “Don’t go out into the fire zone.”

Raunch did not immediately respond to a request for comments by Decrypt.

Why Doom?

Launched in 1993 by id Software, Doom tells the story of a lone space marine who fights his way through a research facility on Mars and into hell to battle hordes of demons. A massive hit among gamers, Doom became a favorite for experimentation when id Software made the source code public in 1997.

Making Doom open-source enabled developers to modify and port the game to countless platforms—from lawnmowers and ATMs to Bitcoin and Dogecoin, and eventually to ChatGPT and even gut bacteria. Whether or not a device can run the iconic shooter has become a fun trend amongst engineers and techie hobbyists, with a dedicated Reddit subreddit for the cause.

“The choice of Doom came from its preexisting reputation of unconventional gameplay,” MIT biotech graduate student researcher Lauren «Ren» Ramlan previously told Decrypt. “I had a great time researching all the wacky devices people had run the game on previously, and wanted to throw my bioengineer hat in the ring.”

Last January, a pseudonymous Dogecoin contributor named Pimax added a playable copy of Doom to the Dogecoin blockchain via its NFT-like protocol, Doginals. Like Bitcoin Ordinals, Doginals lets users inscribe media or content onto the smallest units of Dogecoin, making them permanent artifacts on the blockchain.

The list of devices and platforms running Doom continues to grow. In September, the crypto gaming project RIVES launched the “Doom Olympics,” an on-chain competition on the Ethereum networks Base and Cartesi, with up to $15,000 in prizes.

After watching players quickly figure out how to beat the CAPTCHA, Rauch hinted at future updates.

“I’m tempted to mod it further to make it harder,” he said.

Edited by Andrew Hayward

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