AI Visibility Score: Measuring Website Discoverability Across AI-Powered Search Engines

We introduce the AI Visibility Score (AVS), an open, deterministic scoring standard that combines SEO (30+ checks) and AEO (32+ checks) into a single 0-100 score measuring website discoverability by AI-powered search engines. Through an empirical study of 155 queries submitted to OpenAI's web search API, we collected 816 citations and scanned 721 cited URLs. Findings: (1) median AVS of cited sites is 77 (Grade B), with 59.8% scoring B or above; (2) recommendation queries cite significantly higher-AVS sites (mean 80.2) than local queries (mean 60.0); (3) the SEO-AEO gap is 16 points (80.6 vs 64.5), indicating most websites have not optimized for AI search. Specification, reference implementation, and full dataset are open-source at github.com/ppcvote/avs-standard.