Everyone's writing think-pieces about "optimizing for AI search." I wanted numbers. So I pulled together the 2025-2026 data from Cloudflare, Vercel/MERJ, Ahrefs and the AI providers' own docs. Some of it genuinely changed how I build sites. Here's the reality check, dev to dev.
1. The AI crawlers do not run your JavaScript
This is the big one. A Vercel/MERJ analysis of 500M+ crawler fetches found that none of the major dedicated AI crawlers execute JavaScript — not OpenAI's GPTBot/OAI-SearchBot/ChatGPT-User, not Anthropic's ClaudeBot, not PerplexityBot, not Meta or ByteDance's Bytespider. They fetch your raw HTML and leave. They do download JS files (~11.5% of ChatGPT's fetches, ~23.8% of Claude's) — they just never run them.
The exception is Google: its Web Rendering Service is shared across Search and Gemini, so Google-Extended renders JS the same way Googlebot does.
Translation: if your content only exists after client-side hydration, every AI engine except Google sees an empty shell.
