What is Claude-User? Anthropic's AI crawler

42 of the 389 major websites we measure block Claude-User in robots.txt (11%), making it number 20 of the 30 AI crawlers we track for how often it is blocked. 57 of those sites name it directly in their robots.txt; the rest are covered by a wildcard rule.

Key facts

What blocking Claude-User does

Anthropic says disabling it prevents your content being retrieved in response to a user query, which may reduce your visibility in user-directed web search.

How to allow or block Claude-User

Add one of these groups to the robots.txt file at the root of your domain. It is a stated preference that well-behaved crawlers read, not an enforcement mechanism.

User-agent: Claude-User
Disallow: /

User-agent: Claude-User
Allow: /

Claude-User user agent string

Anthropic's page doesn't list a full string, so look for Claude-User in the user agent field of your logs.

How to verify a request is really Claude-User

Anyone can put a crawler's name in a user agent string, so the name alone proves nothing. Anthropic says blocking its IP addresses may not work correctly or persistently guarantee an opt-out, because that stops it reading your robots.txt. It says to use robots.txt instead.

How to whitelist Claude-User in a firewall or CDN

robots.txt only states a preference. A firewall, CDN or bot protection service can still refuse the request, and the crawler then gets an error even though robots.txt allows it.

1. Check that no group in your robots.txt blocks it, using the rule above.
2. Add an allow rule in your firewall or CDN that matches the name in the user agent. Keep the rule narrow, because anyone can copy a name.
3. Check your server logs for a 200 response from Claude-User afterwards.

On Cloudflare, also check AI Crawler and Agent access policies, which can block search, agent and training traffic across a site.

Why Claude-User gets a 403 or 405 error

A 403 means the server refused the request, which usually points to a firewall or bot rule. A 405 means the server refused the request's method, so check any rule that only permits certain methods. A crawler that obeys robots.txt won't request a page it is told to avoid, so an error in your logs points to your server's configuration. To stop it deliberately at the server, this nginx rule returns a 403:

if ($http_user_agent ~* "Claude-User") {
    return 403;
}

Which sites recently changed their rules for Claude-User?

None that lasted since 17 August 2026. See the full change log.

Who blocks Claude-User, by sector

Sites blocking Claude-User

amazon.com, apnews.com, arstechnica.com, asahi.com, barrons.com, buzzfeednews.com, cnbc.com, cnn.com, cntraveler.com, economist.com, elpais.com, france24.com, globeandmail.com, huffpost.com, imdb.com, instacart.com, investopedia.com, lemonde.fr, lifehacker.com, marketwatch.com, mashable.com, nbcnews.com, newyorker.com, nytimes.com, pinterest.com, quora.com, reddit.com, reuters.com, sciencedirect.com, spiegel.de, telegraph.co.uk, theatlantic.com, theguardian.com, thetimes.co.uk, theverge.com, travelandleisure.com, usatoday.com, verywellhealth.com, vox.com, wired.com, wsj.com, zdnet.com.

Sites that allow Claude-User by name

academia.edu, bestbuy.com, bloomberg.com, disneyplus.com, ebay.com, expedia.com, fastcompany.com, figma.com, flickr.com, forbes.com, hackernoon.com, hulu.com, inc.com, klaviyo.com, netflix.com, omio.com, pcmag.com, render.com, seranking.com, soundcloud.com, spyfu.com, theregister.com, ulta.com, vrbo.com.

Other Anthropic crawlers

Claude-SearchBot (search indexing), ClaudeBot (model training).

See all 30 AI crawlers, the rule change log or the full study. Being reachable is only the first step: how AI search engines choose what to cite covers the rest.

IndexHalo. "Claude-User block rate across major websites." Measured 3 November 2026. https://www.indexhalo.com/ai-crawlers/claude-user/

<a href="https://www.indexhalo.com/ai-crawlers/claude-user/">Claude-User block rate across major websites, IndexHalo</a>