An Eight-Week Analysis of Accept-Language Headers Across Major AI Bots

I logged the Accept-Language header on 51,884 verified AI-bot requests over eight weeks. There is no shared convention. Most training crawlers (GPTBot, ClaudeBot, Applebot, Bingbot, Amazonbot) send nothing. Googlebot sends a bare *. Claude-Web sends a hardcoded en-US,en;q=0.9. Only the live fetchers, ChatGPT-User and part of PerplexityBot, send real quality lists, and those values leak the locale of the human who triggered the fetch. The practical upshot: on a multi-locale site, your default-loc...