AI Surface Visibility refers to the presence and citability of a website, domain, author, or content entity within the output layer of large language models (LLMs). It measures whether content is retrieved, referenced, linked, or cited by AI systems such as ChatGPT, Claude, Gemini, or Perplexity during response generation. High AI surface visibility indicates strong alignment with retriever indexes, semantic embeddings, and trust signals used in retrieval-augmented generation (RAG) pipelines.