ChatGPT

ChatGPT by OpenAI is the world's most widely used AI assistant and the primary platform for GEO testing and optimization. With over 200 million weekly active users as of 2025, it's often the first place brands should check whether they're being recommended in AI-generated answers. For GEO practitioners, ChatGPT serves two roles. First, it's a testing ground: ask it questions your customers would ask and see whether your brand appears. Does ChatGPT recommend your product category at all? Does it mention you alongside competitors? This baseline test tells you where you stand. Second, ChatGPT is a training target. Unlike Perplexity (which uses real-time retrieval), ChatGPT's base model draws on training data. This means content that appeared in high-authority sources before the training cutoff carries significant weight. Getting covered in major publications, Wikipedia, and widely cited research increases your likelihood of appearing in ChatGPT answers. ChatGPT's browsing mode (available in ChatGPT Plus) adds real-time retrieval, behaving more like Perplexity. Optimizing for both the base model (long-term authority) and browsing mode (current content quality) is a complete approach. Key features for GEO: Custom GPT creation for branded experiences, API access for integration into monitoring tools, direct conversational interface for testing brand visibility.