Claude
Anthropic
Links Claude writes in the answer text on claude.ai send
https://claude.ai/ as the referrer: the origin only, with no conversation path. Sites that read the referrer can already count those visits as Claude.4 next improvements
Last checked 2026-10-20
Gemini
Gemini on the web sends
https://gemini.google.com/ as the referrer: the origin only, from source links and from links the user pasted. Its links use rel="noopener" without noreferrer, exactly as recommended. From September 18 to 28, 2026, Gemini links also carried utm_source=gemini (and geminiforbusiness for Workspace).3 next improvements
Last checked 2026-10-20
ChatGPT
OpenAI
OpenAI publishes the
utm_source=chatgpt.com value in its publisher FAQ, and ChatGPT adds it to every outbound link we tested on the web: citations, links in the answer text and links the user pasted. It keeps existing query parameters and inserts the tag before a #fragment. After a UI update in early October 2026, the tag was restored within about a week.4 next improvements
Last checked 2026-10-20