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AI agent · September 2026

ClaudeBot in robots.txt: who blocks it

9.2% of the 166,024 sites in the census name ClaudeBot in their robots.txt, and 86.8% of those block it.

9.2%
Sites naming it

Sites naming it

Sample
n=166,024
Coverage
100.0%

The September 2026 crawl, parsed for a robots.txt rule naming this user-agent, on the same 1% sample of the corpus as every other figure on this site — 166,024 sites. It used to be measured on the whole corpus and this note used to say so; it moved to the monthly sample when the axis gained a series, so it now carries the same margin as everything else.

8.0%
Sites blocking it

Sites blocking it

Sample
n=166,024
Coverage
100.0%
Name it
Name it: 9.2%
9.2%
Block it
Block it: 8.0%
8.0%
0%25%50%75%100%
Of the 166,024 sites in the census, 9.2% name ClaudeBot and 8.0% forbid it. Both bars are the same base, so the gap between them is the sites that named it to let it in.

What ClaudeBot actually does

Run by Anthropic. Crawls to train Anthropic models. Blocking it costs you no traffic: this crawler does not send anyone your way.

What to write in your robots.txt

Put the rule in its own group. A Disallow under User-agent: * predates these agents and several of them do not treat it as applying to them — which is also why this census does not count it.

User-agent: ClaudeBot
Disallow: /
robots.txtTurns ClaudeBot away. Blocking it costs you no traffic: this crawler does not send anyone your way.
User-agent: ClaudeBot
Allow: /
robots.txtLets it through, said out loud rather than by saying nothing. Either way it is a published preference and not a wall: robots.txt enforces nothing.