tl;dr: Decoy Font is a downloadable TTF font that uses the hybrid image technique—thin high-frequency foreground letters overlaid on blurred low-frequency background letters—so humans read one message up close (or when zoomed out) while OCR and LLMs like ChatGPT and Gemini tend to read the decoy. It's derived from DejaVu Sans Mono, free for personal and commercial use, and pitched as an anti-scraping tool, though the author admits smarter agents or targeted prompting can defeat it.