Decoy Font: A Typeface That Hides Messages from AI

Mixfont, a digital font foundry and research lab, has released Decoy Font, a typeface designed to hide messages from artificial intelligence (AI) chatbots. The font exploits a hybrid image optical illusion, layering thin, clear outlines in the foreground with blurry, dark shapes in the background. Humans typically perceive the bold, blurry letters, while AI models, which analyze pixels up close, read the crisp foreground text. This allows users to embed a hidden message for AI that differs from the human-readable text. Founder Eric Lu, an AI researcher, created the font to explore the intersection of AI and typography and to address concerns about data scraping and AI fatigue. In demonstrations, advanced models like GPT-5.6 Sol and Gemini 3.5 misread an image that said "sleep early" as "binge shows." Decoy Font is available as a web application for encoding specific messages or as a downloadable TTF file that produces gibberish for AI. Lu also sees potential applications in CAPTCHA tests and as a benchmark for tracking AI progress. The project builds on Lu's earlier Ghost Font, which used animations to obscure text. Mixfont developed Decoy Font using its own code and the public domain DejaVu Sans Mono as a reference. The font is part of a broader conversation about AI's reach and public trust, with Lu noting that while AI may soon overcome this trick, it serves as a timely benchmark.