Quantcastbot user agent
Operated by Quantcast
Quantcastbot is the crawler of Quantcast's audience measurement and advertising platform.
The Quantcastbot bot at a glance
- Quantcastbot is operated by Quantcast and checks landing pages for an advertising platform.
- The robots.txt token for Quantcastbot is Quantcastbot.
- Blocking a platform fetcher has no effect on organic search rankings.
- Quantcastbot robots.txt support: Not documented.
- Recommendation for Generative Engine Optimization (GEO): Your choice.
What is Quantcastbot?
Quantcastbot reads pages to classify them for audience and ad targeting.
Public registries list it as an advertising crawler.
Should you block Quantcastbot?
Blocking Quantcastbot is a business decision: it protects your content but can lower how well AI products know your brand.
| Effect on search rankings | Blocking a platform fetcher has no effect on organic search rankings. |
|---|---|
| Effect on AI visibility | Blocking breaks the feature the fetcher serves, such as ad approval or feed updates. |
| Follows robots.txt | Not documented |
| Recommendation | Your choice |
How to block or allow Quantcastbot
Put the robots.txt rule in the file at the root of every domain and subdomain, for example https://example.com/robots.txt. The token Quantcastbot is matched case-insensitively. robots.txt alone may not stop Quantcastbot, so add the Nginx, Apache or Cloudflare rule as well.
robots.txt: block
# Block Quantcastbot
User-agent: Quantcastbot
Disallow: /robots.txt: allow
# Allow Quantcastbot
User-agent: Quantcastbot
Allow: /robots.txt: partial
# Keep Quantcastbot out of private areas only
User-agent: Quantcastbot
Disallow: /wp-admin/
Disallow: /cart/
Disallow: /checkout/
Disallow: /my-account/
Allow: /Nginx
# Nginx: return 403 to Quantcastbot
if ($http_user_agent ~* "(Quantcastbot)") {
return 403;
}Apache
# Apache .htaccess: return 403 to Quantcastbot
RewriteEngine On
RewriteCond %{HTTP_USER_AGENT} (Quantcastbot) [NC]
RewriteRule .* - [F,L]Cloudflare WAF
# Cloudflare > Security > WAF > Custom rule, action: Block
(http.user_agent contains "Quantcastbot")How to verify real Quantcastbot traffic
Quantcast publishes no IP list or reverse DNS pattern for Quantcastbot, so the user agent cannot be verified. Anyone can send the same string. Rate-limit unusual volume instead of trusting the name.
How to find Quantcastbot in your server logs
Search the web server access log for the token. The command below counts Quantcastbot requests per URL on Nginx or Apache.
grep -i "Quantcastbot" access.log | awk '{print $7}' | sort | uniq -c | sort -rn | head -20For a full report per AI bot, upload the log to the AI Log File Analyzer, a free tool by Justin Hà.
Quantcastbot user agent string
The full user agent Quantcast publishes for Quantcastbot. Version numbers such as Chrome/W.X.Y.Z change over time, so match the token, not the whole string.
Quantcastbot/1.0 (+http://www.quantcast.com/bot)Quantcastbot FAQ
Quantcastbot identifies itself with the robots.txt token "Quantcastbot". A typical request header reads: Quantcastbot/1.0 (+http://www.quantcast.com/bot)
Quantcast has not documented how Quantcastbot treats robots.txt. Add a robots.txt rule and back it with a server rule if the traffic matters to you.
Blocking a platform fetcher has no effect on organic search rankings. Blocking breaks the feature the fetcher serves, such as ad approval or feed updates.
Add two lines to the robots.txt file at the root of each domain and subdomain: "User-agent: Quantcastbot" followed by "Disallow: /". The token is case-insensitive. Changes can take up to 24 hours to be picked up.
Not reliably. Quantcast publishes no IP list or reverse DNS pattern for Quantcastbot, so anyone can send the same user agent. Rate-limit unusual volume instead of trusting the name.
Search your server access log for "Quantcastbot", for example with: grep -i "Quantcastbot" access.log. The AI Log File Analyzer by Justin Hà counts visits per AI bot from an uploaded log file.
Sources: Public bot registry. Last reviewed by Justin Hà.
See which of these bots actually reach your website
The AI Log File Analyzer by Justin Hà counts visits from GPTBot, ClaudeBot, PerplexityBot and other AI crawlers in your server log, for free. The GEO Technical Package sets up robots.txt, llms.txt and crawler access for AI search.
