Who runs it
OpenAI. It names itself with the token GPTBot.
What it does
It collects pages for model training. It doesn't decide whether ChatGPT can find you: that's OAI-SearchBot, which builds ChatGPT's search index. And when someone asks ChatGPT to open a page, ChatGPT-User fetches it.
Renders JavaScript
Not yet observed. OpenAI doesn't say whether GPTBot runs scripts, and this site hasn't recorded a verified visit yet. A page that needs JavaScript to show its content is a risk for any machine that doesn't say.
How to verify it
Match the visiting address against OpenAI's published list. OpenAI documents no reverse DNS check.
robots.txt
Rules under User-agent: GPTBot apply to it. OpenAI says disallowing it indicates a site's content should not be used to train its models, and leaves ChatGPT search untouched.
Disallow: /
User-agent: OAI-SearchBot
Allow: /
Questions
If I block GPTBot, will ChatGPT stop citing me?
No. Citations in ChatGPT search come from OAI-SearchBot's index and from ChatGPT-User's live fetches.
Does ChatGPT-User follow robots.txt?
OpenAI says robots.txt rules may not apply to it, because a person asked for the page.