Not Pron (or Not Pr0n) hands this fact to you right up front. It's not porn. It's about furthest thing away from porn—it's a site that bills itself as "the hardest riddle available on the internet." And despite starting in July 2004, only 34 people have been given certificates for finishing it. Since last October, only three people were added to that roster.
This is a rather extraordinary figure, when you consider that the internet loves sleuthing. And after solving all 140 levels, you'd think someone would have some inclination to post the answers all over Pastebin and ruin the fun for everyone involved. But somehow, after 11 years, that hasn't really happened.
The game starts you out by clicking a door, but then goes straight downhill. You're modifying URLs, rewriting HTML, translating Morse code, Googling for answers. The creator even recommends that you download external programs to solve some puzzles; some of them on the site even require it.
At 11 years, Not Pron is much older but still distinctly different than the internet puzzles that made headlines the past few years. For instance, the latest cryptic (and frankly, attention-grabbing) riddle that made the rounds involved a Gothic-looking video of a guy in a plague mask flashing threatening messages allegedly aimed at the White House. It had all the marks of a viral marketing stunt: some level of mysteriousness, threatening messages tucked into a sound file, and of course, it's creepy.
Cicada 3301 was another puzzle that worked in a similar fashion—no one knew who made it, or why, but it had people searching light posts in 14 cities, cracking cryptographic codes, and looking at Mayan numerals. Theories floated around saying that the NSA was using 3301 as a recruitment tool. But to this day, no one knows why it was made.
But Not Pron is much more innocuous. The creator isn't some shadowy figure, and you do actually receive a physical certificate from him as well as a secret prize. There's no broader backstory to this. The creator even said he's not really a puzzle person, but it just kept going and kept getting bigger over the years.
In an interview with Fast Company, David Münnich, creator of the site, said that it's impossible to finish the puzzle on your own. He said you'd need an extraordinary set of skills, intimate computer knowledge and a mind wrapped around trivia to do so, and most people who get far in the game do it in groups. Forums are dedicated to cracking those riddles. Some players even contributed riddles, Münnich said.
But unlike Cicada 3301 and the weird plague mask video, Not Pron is just a hard puzzle for puzzle lovers. While it sticks you into a dark house, there's aren't any spooks, conspiracy theories, or associated creepypasta stories attached to it to get you into the zone. There's no real mystery to what the light at the end of the tunnel is: the creator is right there, shining it straight at you. Perhaps that's why so few people have solved it.