Block GPTBot only if you specifically want to opt out of OpenAI training use — blocking it does not affect ChatGPT Search citation eligibility, which is controlled by the separate OAI-SearchBot and ChatGPT-User user agents.
OpenAI's bot documentation is explicit that the three agents serve different purposes. Publishers commonly deploy a mixed policy: Disallow: / for GPTBot (no training), Allow: / for OAI-SearchBot and ChatGPT-User (keep search citation).
The equivalent Google control is Google-Extended for training and standard Googlebot for indexing. The two-agent pattern lets publishers stay indexable while withdrawing training rights.
Trade-offs to weigh. Blocking GPTBot has near-zero effect on ChatGPT Search visibility. It does prevent your content from becoming training data for future OpenAI base models, which some publishers value for competitive or legal reasons. It has no legal weight beyond OpenAI's stated policy — a good-faith control, not a technical enforcement.
Sites that publish paywalled or proprietary content typically block GPTBot; sites optimizing purely for citation exposure usually allow it. There is no wrong answer, only a policy choice.