Nullgen is a free, on-device browser extension that blocks generative AI prompts. Detection runs on the device, so what you type never leaves your computer. It works in Chrome, Edge, Firefox, and Safari, on ChatGPT, Claude, Gemini, and any site with an AI composer. Use it to prevent AI cheating, promote academic integrity, stop shadow AI, or prevent data loss. Pro tier adds management features such as access approvals, policies, provisioning and enforcement for families, schools, and companies.