How to block Cloudflare Crawler
Operated by Cloudflare. The Cloudflare Crawler is a well-behaved crawler that retrieves web content. By default, it self-identifies as a bot, honors robots.txt directives, and cannot bypass CAPTCHAs or bot protection. Used by Cloudflare customers via the Browser Run /crawl endpoint.
How it identifies itself
Cloudflare Custom Hostname Verification
robots.txt
What the agent asks to be told. It obeys this or it does not — nothing enforces it.
User-agent: Cloudflare Custom Hostname Verification Disallow: /
nginx
In the server block, then reload.
# In the server block. 403 rather than 444: a closed connection tells the
# operator nothing, and an agent that gets a status code can log it.
if ($http_user_agent ~* "(CloudflareBrowserRenderingCrawler/1.0|Cloudflare Custom Hostname Verification)") {
return 403;
}
Apache
In .htaccess or the vhost.
BrowserMatchNoCase "CloudflareBrowserRenderingCrawler/1.0" bad_bot
BrowserMatchNoCase "Cloudflare Custom Hostname Verification" bad_bot
<RequireAll>
Require all granted
Require not env bad_bot
</RequireAll>
Cloudflare
Security → WAF → Custom rules.
# Security → WAF → Custom rules, action: Block (http.user_agent contains "CloudflareBrowserRenderingCrawler/1.0") or (http.user_agent contains "Cloudflare Custom Hostname Verification")
WordPress
A child theme's functions.php, or a small plugin.
// functions.php of a child theme, or a small plugin. Runs before WordPress
// builds the page, so a blocked agent costs one PHP process and no queries.
add_action('init', function () {
$agent = $_SERVER['HTTP_USER_AGENT'] ?? '';
foreach (['CloudflareBrowserRenderingCrawler/1.0', 'Cloudflare Custom Hostname Verification'] as $needle) {
if (stripos($agent, $needle) !== false) {
status_header(403);
exit('Blocked: Cloudflare Crawler');
}
}
});
robots.txt is a request. The rules below it are the wall.
Cloudflare Crawler publishes a token, so the directive above will work for as long as it keeps honouring it — and nothing except its own good manners makes it. The server rules match on a header the requester sets, which stops the agent that says who it is and not the one that copies somebody else's name. Botscope verifies identity against DNS and published address ranges, records which check decided each request, and shows you the ones that lied.