What is DuckAssistBot? DuckDuckGo's AI crawler

41 of the 389 major websites we measure block DuckAssistBot in robots.txt (11%), making it number 22 of the 30 AI crawlers we track for how often it is blocked. 44 of those sites name it directly in their robots.txt; the rest are covered by a wildcard rule.

Key facts

What blocking DuckAssistBot does

DuckDuckGo says this data is not used to train AI models, and that disallowing the agent takes effect after 72 hours.

How to allow or block DuckAssistBot

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: DuckAssistBot
Disallow: /

User-agent: DuckAssistBot
Allow: /

DuckAssistBot user agent string

The string DuckDuckGo documents. Version numbers can change, so match on the name.

DuckAssistBot/1.2; (+http://duckduckgo.com/duckassistbot.html)

How to verify a request is really DuckAssistBot

Anyone can put a crawler's name in a user agent string, so the name alone proves nothing. DuckDuckGo publishes the addresses DuckAssistBot uses: duckduckgo.com/duckassistbot.json. Check a request's source address against that list.

How to whitelist DuckAssistBot 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 and the published IP addresses. Keep the rule narrow, because anyone can copy a name.
3. Check your server logs for a 200 response from DuckAssistBot afterwards.

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

Why DuckAssistBot 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 ~* "DuckAssistBot") {
    return 403;
}

Which sites recently changed their rules for DuckAssistBot?

See the full change log.

Who blocks DuckAssistBot, by sector

Sites blocking DuckAssistBot

amazon.com, arstechnica.com, barrons.com, bbc.co.uk, bloomberg.com, buzzfeednews.com, cnn.com, cntraveler.com, elpais.com, fastcompany.com, flickr.com, france24.com, globeandmail.com, huffpost.com, inc.com, instacart.com, investopedia.com, lemonde.fr, lifehacker.com, marketwatch.com, mashable.com, netflix.com, newyorker.com, nytimes.com, pcmag.com, reddit.com, reuters.com, smh.com.au, telegraph.co.uk, theage.com.au, theguardian.com, theregister.com, thetimes.co.uk, theverge.com, travelandleisure.com, usatoday.com, verywellhealth.com, vox.com, wired.com, wsj.com, zdnet.com.

Sites that allow DuckAssistBot by name

academia.edu, delta.com, disneyplus.com, hackernoon.com, hulu.com, imdb.com, klaviyo.com, pinterest.com, sciencedirect.com, squarespace.com, stability.ai, theatlantic.com.

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. "DuckAssistBot block rate across major websites." Measured 3 November 2026. https://www.indexhalo.com/ai-crawlers/duckassistbot/

<a href="https://www.indexhalo.com/ai-crawlers/duckassistbot/">DuckAssistBot block rate across major websites, IndexHalo</a>