Decoy Font is a new TTF font designed to make typed messages difficult for AI to read. It achieves this by embedding a decoy message within each letter, utilizing separate spatial frequencies for foreground and background elements. From a close-up view, AI models typically focus on the clear foreground outlines, missing the hidden message.

When viewed from a farther distance or with squinted eyes, the background, low-frequency mass becomes apparent, revealing the intended message. This technique has proven effective in confusing advanced LLMs like ChatGPT, GPT Sol, and Gemini 3.5.

Derived from Deja Vu Sans Mono, Decoy Font can be used in personal, commercial, and client projects. It's inspired by the hybrid image technique used in optical illusions, such as the Einstein-Marilyn Monroe image, to obscure text from AI and OCR. While not foolproof against sophisticated AI agents, it serves as an effective initial deterrent against casual observation and scraping.

Researchers at Mixfont, the creators of Decoy Font, are exploring further applications, including potential uses in CAPTCHAs and private messaging, and are interested in extending the concept to character-based languages like Chinese. The font is available for download, allowing users to experiment with its anti-AI capabilities.