Reddit confirmed Monday it is using large language models to catch stealth marketing content, flagging 25,000 spammy posts and comments every day. Reddit is the top-cited domain in large language model responses, appearing across ChatGPT Search, Perplexity, and Google AI Mode, according to a Semrush study. OpenAI and Alphabet have content licensing deals with Reddit allowing their AI tools to draw from the platform. A discipline called generative engine optimization (GEO) aims to make a brand appear in AI-synthesized answers by planting convincing Reddit comments. Shanzila Ahmed, whose agency ReachLLM creates Reddit content for GEO clients, confirmed to Bloomberg on Monday that her firm's posts have appeared in ChatGPT responses sometimes within a day of publication, and that some posts have since been removed by Reddit but her firm replaces removed content continuously. A separate company, RedRover, advertises deploying AI agents to mass-publish content across Reddit and blogs, according to 404 Media. Profound, an analytics firm tracking brand visibility in AI responses, topped a $1 billion valuation after a February 2026 funding round, according to Profound's $96M Series C funding.