A developer has created a new typeface designed to be readable by humans but nearly impossible for artificial intelligence to decode.
Called the "Ghost Font," the typeface writes messages using motion rather than static characters. Its creator, Eric Lu, said it uses "a combination of motion, video, noise, and decoys" to share messages with other real humans that AI cannot easily understand.
"I suppose technically, it's not a font in the traditional sense of a TTF font file," Lu said. "But, Ghost Font is an experiment of a way to graphically communicate in writing in a format that AI cannot easily understand. While it's not as legible as regular text, the letters are still immediately readable to a human eye, but even leading AI models can't decipher it easily."
Lu tested the font by feeding leading AI models videos of it, and found that even the most recent AI agents struggled to decode the moving messages.
Lu said his inspiration was ZXX, a typeface created in 2013 by designer Sang Mun that included four fonts designed to be readable by humans but not by optical character recognition software.
"At the time, this font was deemed 'surveillance-proof' but fast forward to today, and modern AI agents can easily read text rendered in ZXX," Lu wrote in a blog post. To get around modern AI bots, he said he had to use motion instead.
Visitors to Lu's blog can type their own message and watch the letters appear through moving dots. "Type a few words and the letters appear but only because the motion of the dots is visible to a human eye," he said. "When the video is paused, the static dots blend together, and it becomes impossible to tell just from looking at a single frame what message is embedded in the image. That means that screenshotting the page won't reveal the message."
A decoy message for extra protection
The Ghost Font also includes a decoy message meant to throw AI bots off track. "The decoy message serves as a final trick for a determined agent," Lu explained. "When looking for a hidden message, it might first find the decoy message and think that that is the real embedded message in the video. That's how Ghost Font is able to hide a message even from the strongest thinking models like Fable and GPT Sol 5.6 Ultra."
Lu said the font could have practical applications, including in CAPTCHA systems. "It would be interesting to incorporate Ghost Font into CAPTCHA systems, as most systems are easily solved by AI today," he said. "Using motion in a video would be a way to make it much more difficult for an automated bot to decipher but still relatively easy for a human to read."
Lu acknowledged that AI models are likely to catch up eventually. "AI is certainly getting really good," he said. "While Ghost Font is hard for AI to read, it's also pretty hard for humans to read! The gap continues to close. It will be interesting to see what the future holds when it comes to AI perception and multimodal models."
Social media users who tried the font this week gave mixed reactions. One person on X asked, "Is this the ultimate CAPTCHA?" Another wrote, "I don't see the point of such efforts, even in the short run before AIs catch up." A third joked, "The only downside is that it drives all who look upon it INSANE."
